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© Raymond Pettibon 





RESEARCH LIBRARY 
Mieeoer! 1 RESEARCH INSTITUTE 


JOHN MOORE ANDREAS COLOR CHEMISTRY LIBRARY FOUNDATION 











PROPERTY OF 
TEGHMIGOLOR MOTION 
PILIURE CORP. 











Glues and Gelatine 


A PRACTICAL TREATISE 


ON THE 


METHODS OF TESTING AND USE 


BY 
R. LIVINGSTON FERNBACH 


CHEMICAL EXPERT 


THIRD PRINTING. 





NEW YORK 


D. VAN NOSTRAND COMPANY 
EIGHT WARREN STREET 
1921 


he 
yo 





ae igs me 





ht, 1906 


Cop 
pe 


§ 


> 
. 





7f 





PREFACE 


THis work purports to be a practical treatise on the 
testing and examination of glue and gelatine. It aims 
to acquaint the consumer with the methods employed 
by representative American manufacturers in grading 
and distinguishing between glues and the considera- 
tions governing their valuation. It offers to the chemist, 
who is too often unfamiliar with these products, al- 
though experienced in other lines, test methods chosen 
with a view to determining the value of a glue for 
a specific purpose, rather than merely defining its 
abstract chemical characteristics. 

While the subject of glue is by no means unrepre- 
sented in technical literature, it has been dealt with 
chiefly from the standpoint of manufacture; while the 
intelligent testing of glue — that which must deter- 
mine its commercial value, and which, furthermore, is 
the only means by which the manufacturer himself is 
enabled to assign a grade and a price to his product, 
has been given scant consideration; the subject being 
dismissed with brief reference to methods at once 
obsolete and inaccurate. 

The futility of attempting a treatise on the manu- 
facture of glue has long been manifest to the author. 
Theory and practice differ radically in the production 
of this article, more so, perhaps, than in the case of any 
other. It has’ been the experience of more than one 

lll 


1V PREFACE 


trained chemist to attempt the manufacture of glue, 
relying for guidance solely upon the chemical principles 
thought to be involved, and the results have been 
ludicrous. ‘Tersely stated, the art of making glue con- 
sists in knowing what to do and how to do it; and this 
state of enlightenment presupposes long study under 
some one who, in turn, acquired the art from an ex- 
perienced teacher. As certain manufacturing methods, 
however, leave clues in the finished product that aid 
in the determination of its commercial value, brief 
reference has been made to the principles underlying 
the manufacture of glue and gelatine. 

Nor do I enter into any protracted discussion of the 
probable constitution of glutin or gelatin and allied 
substances; nor of the chemical changes undergone 
by the glue-yielding materials in the course of manu- 
facture. As enunciated in the contemporary litera- 
ture of the subject, these principles are at best premises 
argued from conclusions — mere opinions that have 
yet to be substantiated in actual practice. They have 
absolutely no bearing upon the fitness or unfitness of a 
glue for a given purpose, nor do they aid either chemist 
or consumer in determining which of two glues is the 
better. - % 

Upwards of fifty million pounds of glue, foreign and 
domestic, are consumed annually in the United States, 
in such industries as the manufacture of veneers, wall 
paper, matches, paper boxes, artificial leather, painters’ 
size, patent sizings, woodwork and a host of others. 
Despite this vast consumption, it is safe to assert that 
80 per cent of glue users have but the vaguest con- 
ception of its properties and are guided largely by the 


PREFACE ‘V 
manufacturer or dealer in the selection of their supply. 
In the main, their confidence is not abused; but in 
many instances they are victims of unscrupulous sales- 
men. Some go through the formality of ‘ testing,” 
employing methods the recital of which would strain 
the reader’s credulity. He who fully understands the 
nature and properties of the material for which he 
annually expends many hundreds of dollars is indeed 
rara avis. 

To afford the uninitiated consumer a rational means 
of protection is the chief aim of this work. It is de- 
signed, also, to aid the chemist unfamiliar with authen- 
tic test methods, whose sole recourse, when appealed 
to for an opinion respecting glue, has invariably been 
analysis, which fails absolutely of the desired result. 
In the interests of the former, I have endeavored to 
describe the test methods in a manner that will permit 
of their accurate execution by any one of intelligence. 
At the same time, I have been at pains not to deprive 
them of their technical character in order that the 
chemist may appreciate their adaptability to the re- 
quirement of the average commercial laboratory. 

The day is not far distant when glue and gelatine 
will be purchased on specification; and such a trade 
condition will necessitate the adoption of a uniform 
system of tests throughout the United States. In the 
interval, it is the earnest hope of the author that the 
suggestions herein contained may serve to reduce to 
the semblance of uniformity the present widely diver- 


gent processes for the assay of glue and gelatine. 
R.L.F. 


Paterson, N. J. 
March 8, 1906 


“ 





TABLE OF CONTENTS 


CHAPTER I 
INTRODUCTORY. PAGE 
Nature and Properties of Glue — Sources of Glue — 
Principles of Manufacture—-Commercial Forms . . . 1 
CHAPTER II 


CLASSIFICATION AND TESTING OF GLUES. 


Preliminary Considerations — Standards — The Cooper 
Grades — Test Methods — Examination of the Dry Glue 
— Sampling — Odor of the Glue Solution — Alkalinity 
and Acidity — Grease — Viscosity — Value of Viscosity 
as a Test Factor — Foam — Jelly Strength — Shot Test 
— The Finger Test — The Test System as a Whole — 
Apparatus Required — Procedure — Selection of Stand- 
ards — Weighing out the Glues — Softening or Soaking 
the Glues — Melting the Glues — Order of Seeking the 
Test Factors — Jelling or Cooling the Glues — Recording 
the Test —- Testing of Gelatine— Tables . . . . . 20 


CHAPTER III 


ANALYSIS OF GLUES AND GELATINES. 


Relation of Analysis to Testing — Determination of 
Moisture — Determination of the Ash — Acidity and 
Alkalinity — Determination of Mineral Acid — Deter- 
mination of Free Organic Acid — Estimation of Grease 
or Fat — Properties of Constituent Elements — Gelatin 
and its Preparation — Reactions of Gelatin — Chondrin 
and its Preparation — Reactions Distinguishing Chondrin 
from Gelatin — Estimation of the Glue Content — Com- 
parison of Direct and Indirect Methods — Estimation of 
Foreign Matter — Characteristic Reactions of Glue and 
Gelatine — Qualitative Estimation of the Purity of Com- 
SIE SCREEN Or 5s: fale ng poet Rohe) nee eer ge EY OD 

vii 


viii TABLE OF CONTENTS 
i 


CHAPTER IV 


GLUE AND GELATINE SUBSTITUTES. PAGE 
Casein — Egg Albumin — Blood Albumin — Japanese 
Gelatine — Dextrine Crystals — Gum Crystals — “ Liquid 

Glue’’ — Methods of Detectionand Analysis . . . . 72 


CHAPTER V 
ForEIGN GLUES. 
English Glues — Irish Glues — Scotch Glues — Ger- 
man Glues — French Glues — Italian Glues — Compari- 
son of Foreign and Domestic Glues . . . . . . 86 


CHAPTER VI 


SELECTION OF GLUES FOR VARIOUS INDUSTRIES. 
Glues for Jomer Work— Glues for Wall Paper — . 
Glues for Surface-Coated Papers —Glues for Paper Box 
Making — Glues for Sizing Purposes — Glues for Textile 
Industries — Comparison of Mixed and Straight Ground 


Glues — Glues for Matches . 2)... ) lope eee 
CHAPTER VII 
How Guius SHoutp BE Usep .  . 2. 4 eee 


CHAPTER VIII 


COMMERCIAL AND LEGAL ASPECTS. 
Trade Conditions Affecting the Price of Glue — Posi- 
tion of the Jobber in the Trade — The Consumer’s Re- 
dress in the Law =.) 2) 0.) $a) st De ee 


CHAPTER Ix 


MANUFACTURING RECEIPTS. 


Water-proof Glues — Mending Cements — Flexible 
Glue and Padding Composition — Liquid Glues — Pre- 
pared Size — Analysis of some Products of which Glue is” 
a Constituent... . >. & 4) 2 2 SR 


TABLE OF CONTENTS 1s 


CHAPTER X 
ANALYTICAL METHODS. PAGE 
Desiccation — Weighing — Filtration — Washing Pre- 
cipitates — Drying Precipitates — Incineration of Filters 
RETR) se ee iw el wet vw et, AZB 


APPENDIX. 


Preparation of Reagents — Standard Solutions — Com- 
parison of English and Metric Weights and Measures — 
Comparison of Specific Gravity and Degrees Beaumé — 
Comparison of Thermometers — Table of International 
eV CIO as. ks se ce tw sl ee 298 





% 


CHAPTER 1 
INTRODUCTORY 


1. Nature and Properties of Glue.—2. Sources of Glue.—3. 
Principles of Manufacture. — 4. Commercial Forms. 

1. Nature and Properties of Glue. — Through laxity 
of usage, the term “glue,” from “gluere — to draw 
together’? — has been extended to include all solutions 
of substances exhibiting binding or adhesion. Its legit- 
imate application comprehends only those viscous 
adhesive bodies resulting from the treatment of animal 
bones or tissues, as well as the bladders and certain 
membranes of fish. These products possess the prop- 
erty of absorbing cold water in quantity, which softens 
them and causes them to swell, when, by the aid of 
heat, they are rendered soluble in the absorbed water, 
from which solution they gelatinize or form a jelly, 
_ after standing and cooling for a short time. 

Of itself, this property of gelatination is not sufficient 
to distinguish true glues, animal or fish, from the mass 
of vegetable agglutinants, the solutions of which are 
often erroneously classified as glue. All starches ge- 
latinize upon treatment with boiling water, the soluble 
varieties first forming a clear solution from which they 
subsequently jell, much in the same way as glues. 
Solutions of Irish moss, agar-agar, ‘Japanese gela- 
tine” and gelose gelatinize upon cooling, and gum 

1 


2 GLUES AND GELATINE 


tragacanth will absorb large quantities of water in 
the cold, forming a gelatinous paste similar to the 
jelly of a weak glue. 

It is in the behavior of the jellies, as well as in the de- 
portment of true glue towards certain chemical reagents, 
that we find a means of distinguishing the true from 
the false. Thus, if the glue jelly be dried, we procure 
practically the original hard glue, which can again be 
soaked up, melted or dissolved, and from this solution 
it will gelatinize a second time. This operation may 
be repeated a number of times. Each treatment, how- 
ever, so impairs the power of gelatination, that a point 
is reached where the glue goes into solution but refuses 
to jell. On the other hand, the products which result 
from drying out the solutions or jellies of starches and 
vegetable gums, are dissimilar to the originals; and, 
while they permit of softening by soaking in cold water, 
no amount of heating will bring them into permanent 
solution a second time. 

The chief constituent of all glue, that which, in the 
main, imparts to it the property of gelatination, is 
GELATIN, or, as it is called by some, GLuTIN. The 
latter term is somewhat objectionable, as it is synony- 
mous with GLIApIN, the essential principle of wheat 
and other starches. While it is true that the analysis 
of purest GELATIN corresponds markedly with that of 
GLIADIN or GLUTIN, this does not justify the assump- 
tion that the nitrogen, carbon, hydrogen, oxygen and 
sulphur, which both contain in corresponding amount, 
are combined in exactly the same way in each. 

According as to the nature of the materials selected 
for the preparation of the glue, there are associated 


INTRODUCTORY 3 


with GELATIN such substances as CHONDRIN, which is 
derived from chondrinogen, the characteristic cartilage 
of young bones and tissues; and KERATIN, from the 
horns of animals. These substances are more viscous 
and adhesive than GELATIN, while displaying less gelati- 
nizing power. Muctn, a slimy substance present in 
the intercellular structure of cartilages, is frequently 
found in glue. It has some adhesive, but little or no 
eelatinizing properties, and its presence must be regarded 
as the evidence of faulty manufacture. 

As the ratio of the GrLatrin to the other substances 
present increases, so does a glue advance in the scale 
of purity; and those hard, glassy products, ranging in 
shade from dark through pale yellow to colorless, are 
the gelatines of commerce. They are refined glues and 
are prepared from stock known to be rich in those 
elements yielding chiefly GkLATIN and but little else, 
1.€., the epidermis and carefully selected bones. These 
undergo special processes with a view to eliminating 
the other constituents of glue. 

’ It is difficult to define the exact point of transition 
from glue to gelatine. The two classes of substance 
possess in common the properties of water absorption 
and subsequent gelatination. The strength of the jelly 
is not a determining factor, many glues being far 
superior in this respect to gelatines. Commercially, the 
distinction is based largely upon the appearance of 
the product. Gelatines are usually transparent or at 
least markedly translucent. Their solutions and jellies 
are very clear. The wiscosity of gelatine solutions — 
that is, their rate of efflux from a vessel of known 
capacity as compared with that of the same volume of 


+ GLUES AND GELATINE 


water, is considerably lower than the viscosity of a 
glue of corresponding strength. This may be ascribed 
to the fact that the CHONDRIN associated with GELATIN, 
in glue, imparts to it the added degree of viscosity. 
The very processes which serve to eliminate the binding 
and viscous elements of glue stock, thereby producing 
gelatine, debar the latter from use as glue; and, con- 
versely, the presence of these elements in glue classify 
itassuch. An intermediate product, known as gelatine- 
glue, displays some of the properties of each and often 
serves as a gelatine, and, again, finds frequent appli- 
cation where glue is required. 

In their deportment towards certain chemical re- 
agents, both GELATIN and CHONDRIN display marked 
characteristics. These reactions, an account of which 
will be found under the chapter on Analysis, appeal 
chiefly to the chemist, in that they furnish some clue 
to the constitution of these substances. They are of 
little interest to the general consumer, as they do not 
enter into the commercial testing of either glue or 
gelatine. Tests based upon them are found to be 
inaccurate and, save for alkalinity or acidity, the 
chemical properties of glue are not factors in rational 
systems of test. 

2. Sources of Glue. — The hides, horns and bones of 
cattle ; the skins of the sheep, goat and pig, as well as 
the bones of some of these; the ‘‘sounds”’ or air-bladders 
and other membranes of fish, constitute the chief stock 
from which glue is derived. Rabbit skins yield a very 
strong glue, of unpleasant odor, which was formerly 
marketed in the form of a jelly, or size. Parchment 
yields considerable glue of high quality. Excepting, 


INTRODUCTORY 5) 


perhaps, clippings from old gloves, leather is not avail- 
able as glue stock, as it is difficult to separate the glue 
from the tanning materials in combination with it. 

Of the above-mentioned hides and skins, only those 
portions rejected by the tanner as unfit are employed 
as glue stock. The better portions are converted into 
the respective leathers, and only the splits and pieces, 
the ears and head portions, and the muscular tissue con- 
tiguous to the skin, known as “‘fleshings,’’ come to 
the glue-maker. The epidermis and carefully selected 
bones comprise stock for gelatine which, in addition, 
is frequently derived from old buttons and similar horn 
products. 

3. Principles of Manufacture. — In the selection of 
the stock for glue making, the manufacturer is called 
upon to exercise considerable ingenuity; and, while the 
subsequent stages of preparation are no less important, 
the greatest care in cooking or treating will not over- 
come the more radical defects of the stock. Glue is 
not merely the solution of the materials present in the 
stock, these being greatly modified by the action of 
boiling water. The exact nature of the change is but 
little understood, but is assumed to be that of hydro- 
lysis —1.e., the addition, chemically, of a certain num- 
ber of molecules of water to the glue-yielding elements. 

Almost any stock, upon treatment with boiling water, 
will yield some glue, but very little. To facilitate the 
extraction and, more particularly, to insure the maxi- 
mum yield, the stock undergoes treatment preliminary 
to boiling, varying in character and duration with the 
nature of the materials selected. : 

In the manufacture of glue from hides or skins, the 


6 GLUES AND GELATINE 


first step is LIMING, or treating the stock with weak 
solutions of lime. Its object is, first, to dehair the 
hide; secondly, to cause it to swell or “plump,” bringing 
the pores to a condition which insures not only the 
rapid extraction of the glue, but also the extraction of 
the maximum amount; thirdly, liming is intended to 
rid the hide of substances which, if present in the 
finished glue, impair its value. 

The operation is conducted in shallow, rectangular 
vats of wood. The stock is immersed in the lime 
solution and stirred from time to time, at which inter- 
vals it is examined and the conditions of the pores 
noted. Some varieties of hide stock require longer 
liming than others. By far the greater quantity of 
hide stock has been limed to some extent before reach- 
ing the glue-maker. The tanner subjects the skins to 
the action of lime, because, like the glue-maker, he 
desires to rid them of all deleterious material and to 
“plump” them, bringing the pores to a condition where 
they will properly respond to the action of the various 
tannins., The tanner’s liming process completed, he 
then rejects those portions unfit for leather, but rich in 
glue-yielding elements, and hence these come to the 
glue-maker partially limed. Where tannery and glue 
factory are in close proximity to each other, the stock 
is delivered in the wet state. In other cases, it is dried 
and then shipped. 

The glue-maker is under necessity of subjecting the . 
stock to further treatment with lime in order to prepare 
it properly. Heavy hide pieces, notably those from 
steers, which are rich in glue-yielding material, fre- 
quently undergo six weeks’ liming, while sheep stock 


INTRODUCTORY 7 


receives little or no further treatment; this, of course, 
assuming that it has been delivered from the tannery, 
as otherwise it receives considerable liming. Goat 
stock is subjected to the process for a period ranging 
from twenty-four hours to ten days. In this there is 
no hard and fast rule, the individual preference of the 
glue-maker being a factor of considerable importance. 

The liming of glue-stock is an operation of great 
delicacy. In the endeavor to rid the stock of non- 
gluey material, and to bring the pores to the proper 
condition, the operation may easily be carried too far 
and much glue-yielding substance be lost through solu- 
tion in the alkaline waters. Over-liming creates de- 
fects in the stock, which cannot be overcome in the 
subsequent stages of manufacture, no matter how care- 
fully conducted. The result is that the finished pro- 
duct is inferior and unfit for the majority of usages. 

Liming finished, it is the practice of some manufac- 
turers to kill excess of lime by means of sulphuric 
acid, converting it into insoluble calcium sulphate. 
Others, again, wash out as much of the lime as possible, 
permitting the balance to remain. As a result, the 
finished glue is more or less alkaline in reaction. While 
moderate alkalinity is of no material disadvantage, 
interfering in no way with tensile strength, it is prefer- 
able to have the glue slightly acid, inasmuch as the 
bacteria which effect the decomposition of a glue jelly, 
thrive in an alkaline medium, whereas in an acid one, 
they have a much harder struggle for existence. Hence 
the solution and jelly of an acid glue keep better and 
longer, independent of artificial preservatives, than those 
of an alkaline glue. 


8 GLUES AND GELATINE 


In the course of liming, some of the grease inherent 
in the stock is converted into insoluble lime soap, the 
subsequent treatment with acid destroying this; and, 
while the mineral salts wash out, the separated fatty 
acids remain in the stock. They have a disagreeable 
odor and must be removed, else the finished product is 
too greasy. Their removal is usually effected in the 
course of boiling, when they rise to the surface of the 
liquor and are skimmed off. 

After liming, the stock is washed. This must be 
done carefully, lest some glue-yielding material be lost. 
Washing frees the stock from excess of lime, where 
treatment with acid has not been resorted to for the 
purpose. It further serves to remove from the stock 
substances which have only been softened and not 
dissolved by the lime. In washing, the stock is sub- 
jected to the action of a stream of water, while a roller 
passes over it, squeezing it out thoroughly. The water 
employed for washing, as well as for boiling, is the 
subject of special consideration. It must be free from 
all salts or chemicals which may interfere with the 
production of a good glue, or tend to precipitate the 
glue from solution. 

Where bones constitute the glue-stock, the simplest 
treatment consists in comminuting them in a suitable 
mill and then steaming the mass to rid it of the bulk 
of grease. In many instances the grease is extracted 
by means of some hydrocarbon solvent, special ma- 
chinery, designed for the recovery of both solvent and 
grease, being employed. Where selected bones con 
prise the stock, they are treated with weak alkali stc 
cleanse them and are then leached with acid for ak 






INTRODUCTORY 9 


period. The object of this treatment is manifest, and 
to understand its operation it is but necessary to recall 
the experiment of childhood, in which a chicken bone 
was softened by means of dilute acid, tied into a knot, 

~ and once more hardened by immersion in lime-water. 
Bones consist of the phosphates of calcium and mag- 
nesia, supported by a framework of cartilage. The 

_ acid dissolves out the mineral salts, leaving the skeleton 
of cartilage, which is the glue-yielding substance. This, 
after careful washing, is subjected to boiling. As with 
hide stock, this washing must be thorough. If the 
bones have not been previously degreased, some of the 
fat is converted into acid soaps. The crude treatment 
of common or ‘‘junk”’ bones, as outlined, results in 
the ordinary bone glues of commerce; while the product 
of leached stock is known as ‘“‘acid-treated”’ bone glue. 
Where the stock has been carefully selected and manip- 
ulated, bone gelatine is produced. 

It is the practice of many manufacturers, prior to 
boiling, to blend different hide stocks after they have 
been limed and washed. Herein lies one of the great 
secrets of making good glue. Sheep stock and goat, of 
themselves, yield exceptionally strong glues, though 
rather greasy. Combined with fine ox fleshings, hide 
pieces ete., the resultant glue is vastly improved in 
strength and in quality, all other manufacturing fac- 

tors being equal. As a result, the bulk of hide glue 
in the market is not ‘‘straight’’ — that is to say, it is 
not made from any one exclusive hide stock, but from 
: ires of two or more. Straight sheep glue is quite 
common, but straight goat is rarely, if ever, met with. 
_ Many of the cheaper grades of glue consist of mixtures™ 





10 GLUES AND GELATINE 


of hide and bone. In preparing these, the respective 
stocks are not mixed beforehand, but are extracted 
separately, the resultant liquors combined in different 
proportions, and the process carried to completion. 
Similarly, liquors extracted from different hide stocks 
may be combined before jellying, although it is by far 
commoner practice to mix the initial dry stocks, as 
previously pointed out. 

In the preliminary treatment, all of the grease in 
the stock is not converted into soap by lime or acid. 
Indeed, only a small portion is so modified, and the 
bulk must be removed by other means. This is usually 
done in the course of boiling, when the grease and 
separated fat rise to the surface of the liquor and are 
skimmed off as closely as possible. Contrary to popular 
belief, the glue-maker is at especial pains to recover 
most of the grease. Apart from the fact that its pres- 
ence, in excess, is hurtful to the finished product, 
barring it from certain uses, the manufacturer has 
often to rely upon its recovery and sale to reduce the 
cost of the glue. Experienced consumers often remark 
that their favorite grade is at times greasier than at 
others. We account for this in the fact that at times 
the price of grease is so low as not to warrant the addi- 
tional laber-cost attendant upon its recovery. In times 
of scarcity, however, the manufacturer, by recovery 
and sale of the grease, realizes an increased margin of 
profit. 

Boiling or Extracting the Stock. — The prepared and 
washed stock is now subjected to boiling or extraction; 
and if the initial treatment is of importance in pro- 
curin rood product, this is noeless so. Here, again, 


3 
« 











INTRODUCTORY 11 


the individuality of the operator asserts itself and, 
while certain fundamental principles are universally 
observed, it is safe to-assert that no two glue-makers 
proceed in exactly the same way throughout, each 
having his little secrets and tricks of the trade. 

The stock may either be dried and stored for a time, 
when it must again be softened prior to extracting, by 
immersion over night in pure cold water, or else it is at 
once placed in the boiling vats. These vary in con- 
struction from simple wooden vats fitted with a steam 
coil and vent for discharging the liquors, to complex 
iron kettles equipped with apparatus for temperature 
control and agitation, and provided with both jacketed 
and direct steam. The stock to be extracted is covered 
with water and the cooking begun. At this juncture, 
two alternative methods present themselves. The oper- 
ator may thoroughly extract the stock in one operation 
and complete the glue from the resulting liquor, or, as 
- is often done, he may produce his glue liquor in “‘runs” 
that is, he begins the cooking using very little water 
and at the minimum temperature necessary for the 
extraction of glue; and, maintaining this for a short 
time, he withdraws the liquor which constitutes the 
first “run.’’ More water is now added, and the cooking 
“continued at an increased temperature and for a longer 
time, and so the second run is produced. According 
to the nature of the stock and the preference of the 
operator, as many as five runs may be obtained, the 
last at the maximum temperature, practically that of 
boiling water, in order to insure complete extraction. 
Prolonged heating is injurious to solutions: of glue, 
gradually destroy ng the gelatinizing power, and, for 


12 GLUES AND GELATINE 


this reason, where glue is produced in runs, the first is 
the strongest as it contains the bulk of choice material, 
extracted at a low temperature. Each succeeding run 
is weaker, the last having but little strength, owing to 
the conditions under which it is produced. 

In the course of boiling or extraction, the preserva- 
tion of the liquor and thus, ultimately, of the finished 
glue, receives attention. For antiseptic and preserva- 
tive purposes a number of substances may be employed 
with varying degrees of success. Chief among these is 
carbolic acid, though this, as a rule, is barred because 
of its characteristic and permeating odor. Formalde- 
hyde is a splendid preservative, but its use, also, is 
attended by disagreeable features. It tends to precip- 
itate a constituent element of the glue and, while its 
operation may not be manifest throughout the processes 
of jellying and finishing, at a later day the consumer, 
in melting the finished glue preserved by its use, is 
confronted with the rather startling spectacle of the 
glue solution separating. Formaldehyde is extensively 
employed as a temporary preservative of very dilute 
bone liquors which are to be concentrated by evapora- 
tion, during which most of the formaldehyde passes 
off as vapor, the final preservative being then added to 
the concentrated liquors. Salicylic and hydrofluoric 
acids are most useful as glue preservatives, the latter, 
although difficult to handle because of its corrosive 
properties, being a powerful germicide. Sulphate of 
zinc has some preservative properties and is often used 
in conjunction with other substances. 

While still in the form of liquor, the glue may be 
subjected to the action of bleaching agents, where a 


INTRODUCTORY 13 


very pale finished product is required. The bleaching 
is usually effected by means of sulphurous acid which 
is conducted in the gaseous state through the hot glue 
liquor. from time to time a sample is withdrawn, and 
the process is terminated when the desired shade has 
been achieved. The color may be improved by the 
addition of such substances as zinc white (oxide of 
zinc), chalk or finely divided barytes or tale. One or 
more of these is added to produce a perfectly white or 
“opaque” glue. Again, only a limited amount of these 
substances may be added, when the resultant glue is 
described as “‘colored.”’ 

As has been stated, the temperature at which the 
glue is extracted requires careful regulation. Bone and 
other liquors are often produced so dilute that they 
will not jell sufficiently to permit of proper cutting, 
and must be concentrated by evaporation. Under 
normal conditions the degree of heat required to effect 
proper concentration would gradually destroy the ge- 
latinizing power of the glue. To overcome this, the 
operation is carried out in a vacuum evaporator. 

Jelling the Glue Liquor. — The glue liquor, from one 
run or several, is conducted from the vat into oblong 
pans or molds with slightly sloping sides and about 
one foot deep. These are then placed in the cooling 
room, where the liquor gradually sets to tenacious jelly. 
These jellies, in the form of oblong blocks, are next 
conveyed to the cutting room where they are sliced. 
The simplest device for cutting consists of two uprights 
permanently fastened upon a long board or runway, to 
the sides of which are attached boards equal in height 
to that of the jelly-block to be cut. These prevent the 


14 GLUES AND GELATINE 


jelly from slipping or swerving. Between the uprights 
stretch fine wires, the space between which may be 
increased or diminished at will. The space between 
the two upper and two lower wires is smaller than 
that between the others, in order that the top and 
bottom slices shall be thinner than the rest. The block 
of jelly is placed in the runway and is firmly pressed 
against the wires, which traverse it longitudinally, 
cutting it into sections which average a half inch in 
thickness. In many plants, more elaborate cutting 
apparatus, operated by power, is employed; but these 
complex types are but amplifications of the principles 
embodied in the simplest. 

Drying the Cuttings. — The sections or cuttings are 
now placed upon nets, made either of galvanized iron 
wire or fish twine, to dry, in a room set apart for this 
purpose. This room is heated artificially and fans con- 
vey the heated air over the nets. In many instances, 
the drying is effected by simply exposing the cuttings 
to natural air currents. In the operation of drying it 
is possible to undo, through carelessness, much, if not 
all, of the good accomplished in the previous stages of 
manufacture. Too much heat, in drying, is as fatal to 
a good product as in boiling and cooking. On the 
other hand, if dried too slowly, the cuttings are apt to 
rot. Some manufacturers rid the cuttings of the bulk 
of moisture by subjecting them first to artificial drying, 
and then finish them by exposure to the air. This is 
thought to ‘‘season”’ the glue. Natural drying in very 
cold weather is productive of frozen glue, much of 
- which comes into the market at intervals. 

The grease which fails to rise to the surface of the 


INTRODUCTORY 15 


liquor in the course of boiling, and so fails of removal 
by skimming, presents itself in the glue jelly and is to 
be found chiefly at the top and bottom of the Jjelly- 
block. For this reason the top and bottom cuttings 
are not, as a rule, spread upon the nets to dry, but are 
set aside and remelted with the next boiling of glue. 
There are times, however, when they are dried with the 
rest, and come into the market under the name of 
Greasy Tops and Bottoms. In the majority of instances 
where the manufacturer goes to the trouble of drying 
these greasy sections, he grinds them to be mixed with 
other ground glues. 

4. Commercial Forms. — As taken from the nets 
when dry, glue is in the form of oblong sheets of vary- 
ing thickness. The. majority of foreign glues come to 
this market in this form, or-as square cakes, the latter. 
very thick. Few, if any, domestic glues are marketed 
in cake form. Gelatines are for the most part sold in 
the sheet. Prior to packing in barrels, the sheets of 
glue are broken into small, irregular pieces known as 
flakes, and hence this form acquires the designation of 
FLAKE GLUE. These may be GROUND, or even POW- 
DERED. Certain glue jellies are cut into long, prismatic 
strips, which, when dry, are slightly twisted and bear 
a faint resemblance to noodles, whence the name, 
NOODLE or STRIP GLUE. Glue jellies are at times so 
cut as to dry to a strip one inch wide by six long, and 
from one quarter to one-half inch thick. This form is 
known as RIBBON GLUE. 

Gelatines are met with in the FLAKE, SHEET, STRIP, 
GROUND, and POWDERED forms. SHRED GELATINE Is in 
the form of fine sections similar to shredded cocoanut. 


16 GLUES AND GELATINE 


The bulk of gelatine consumed here is of foreign manu- 
facture, and is in the sheet form. 

The form of a glue bears no relation to its tensile 
strength or working qualities. It is merely a question 
of individual preference based, perhaps, upon what the 
consumer has been accustomed to use, that impels one 
to employ nothing but flake, where another will use 
only ground or strip. Facility in use is dependent upon 
the form of the glue. A thin-cut flake soaks up faster 
than a thick-cut, a ground glue faster than a thin-cut 
flake, and powdered glue fastest of all. The chief 
objection to foreign glues is that the majority of cheaper 
erades are so thick-cut as to require long soaking before 
they can be melted. 

Flake glues are cut in varying thicknesses. The 
stronger varieties are cut very thin, and where this has 
been done unskilfully the glue is curled up. To pre- 
vent this, the glue liquor is made as dilute as is consist- 
ent with proper jellying and rather thick sections cut 
from the jelly. These consist chiefly of water which 
passes away in the drying, leaving a thin, dry glue; 
and as the drying is conducted somewhat slowly, the 
curling of the edges does not occur. It is readily seen 
that this method is applicable only to a very strong 
glue liquor, as otherwise the necessary dilution would 
interfere with the formation of a jelly sufficiently firm 
to cut. 

Two other forms of glue are produced, Thimble or 
Teat, which has its origin in the fact that weak glue 
jellies frequently drip through the interstices of the 
net, particularly if the drying room become unduly 
warm. Another, SERRATED GLUE, is produced by fore- 


INTRODUCTORY Le 


ing the glue jelly through an apparatus similar to a 
colander, with the result that the dried particles are 
no longer than a quarter of an inch, and twisted. This 
latter form is very rare, and Thimble glue is usually 
promptly ground. 

In the trade, the term “‘opaque”’ is used with refer- 
ence to the presence of coloring matters in the glue, 
rather than as the antonym of ‘‘transparent.” If the 
hard glue be white or almost so, it is called ‘‘opaque’’; 
and if only whitish, ‘‘colored.”’ When materials are 
added to the glue to produce color, an inspection of 
the dry piece may fail to reveal their presence; yet the 
solution will be more or less whitish. The cheaper 
white glues, much prized by the house-painter, are 
made from pig stock, to which an inferior quality of 
coloring material is added. Of this class the North- 
western No. 1, No. 2, and No. 3 are types. High- 
gerade glues are rendered perfectly white or opaque by 
-_ means of zinc white. This adds to the cost of the 
product. Not all liquors can be converted into opaque 
dry glues; only such as have an initial light color re- 
ceive the treatment and are, in addition, bleached 
prior to the admixture of coloring agents, in order 
that only the smallest quantity of the latter need be 
used. The price of opaque glues is always somewhat 
higher than that of clear glues of corresponding 
strength. It is assumed by some that the presence 
of coloring matter in glue is an aid in drying. Prac- 
tice fails to sustain this theory. 

Of the high-grade hide glues, many are cut very 
thin and are almost transparent. Others, again, are 
thicker in section and less flexible. As has been stated, 


18 GLUES AND GELATINE 


these conditions have no bearing upon the strength of 
the glues, save within limits hereafter to be defined. 
As appearance, however, is a material factor in selling, 
glues are made as nice-looking as possible, 

Fish Glues. — With the exception of isinglass, which 
is prepared chiefly from the swimming-bladder of the 
Russian sturgeon, and which is marketed in various 
solid forms such as sheet, purse, lump, pipe, honeycomb, 
etc., fish glues are in the form of heavy solutions or 
pastes. They are all powerful adhesives having the 
characteristic odor of fish, combined with that of the 
materials used to preserve them in the liquid or fluid 
state. To offset this, they are perfumed with essential 
oils (sassafras and wintergreen); but these disguise the 
natural odors only to limited extent. 

Isinglass is a very hard, transparent and practically 
colorless substance. It is the most powerful adhesive 
known and is used chiefly by brewers and wine mer- 
chants for clarifying purposes. It is to be remarked 
that pure gelatine, which is chemically the same thing 
as isinglass, cannot be used for this purpose. Many 
substitutes for isinglass are offered for sale, but they 
possess only to a slight degree the excellent properties 
of the genuine 

Similarly, liquid fish glues are extensively imitated. 
Weak animal glues treated with mineral acids or other 
agents to destroy their gelatinizing power, and per- 
fumed with various essential oils, are sold as fish glues. 
They do not and cannot supplant the genuine, as they 
are deficient in adhesiveness and binding properties. 
In fact, only very weak animal glues will respond to 
the necessary treatment, and these, in very cold weather, 


INTRODUCTORY 19 


jell and must be remelted with the aid of vinegar before 
they can be used. They are properly known as liquid 
glues; and only such as preserve their fluidity at all 
times are deserving of the title. The most: recent 
addition to this class is a weak animal glue treated with 
chloride of calcium which tends to prevent jellying. 
This is the most spurious of all, as this chemical is 
markedly hygroscopic and interferes with complete 
drying. | 

The ‘liquid glue” of the paper-box manufacturer 
contains no glue whatever, being a solution of certain 
grades of corn dextrine. Flour paste is often added 
to increase the body of the material and, incidentally, 
the margin of profit. 

The various mending cements are prepared from glue, 
gelatine and, at times, casein. The glue and gelatine 
are treated with a view to prevent jellying and mixed 
with other substances which render the dried material 
more or less water-proof. 

Flexible glue, for book-binders’ use and for making 
pads or writing tablets, comes in the form of oblong 
cakes, about ten pounds in weight. It is a mixture of 
glue, glycerine and water, the glue being dissolved in 
the regular way and the glycerine then added to impart 
flexibility. Printers’ rollers are made in much the same 
way. Flexible glue is made of white glue or the ordi- 
nary shades. That intended for use as padding com- 
position is colored to suit the consumer, fuchsine 
(magenta) being chiefly employed. Flexible glue is 
frequently worked up into small toys, such as the 
grotesque heads displayed for sale by street fakirs. 


CHAPTER II 


CLASSIFICATION AND TESTING OF GLUES 


Preliminary Considerations. — It is obvious that the 
manufacturer, in assigning a price to the finished glue, 
must reckon with the cost of stock, labor, ete. Theo- 
retically, he might base the price upon these considera- 
tions alone; but, since the most expensive stock may, 
through faulty treatment, yield a weak or inferior 
finished product, he cannot, in practice, be altogether 
governed by the cost of production. In addition to 
the latter, the quality of the product must be consid- 
ered, and the measurement of quality necessitates the 
formulation of a system of test. Glue is sold on “‘test”’; 
that is, the price of the product is governed by its 
strength and certain other properties, for the measure- 
ment of which many divergent tests have been formu- 
lated. Some call for the determination of the exact 
content of GELATIN, since, as a rule, the greater this 
content, the purer and, in some instances, the stronger 
the glue. The methods formulated for this assay are 
faulty and inexact; but, apart from this, the content 
of GELATIN has absolutely no bearing upon the com- 
mercial fitness of the product. Some take note of the 
amount of cold water absorbed by the glue in a given 
time. Others, again, are concerned with the breaking 
strain of the dry glue. It is to be observed that such 
test methods as are limited to the determination of 

20 


CLASSIFICATION AND TESTING OF GLUES © 21 


only one constant or property are deficient in scope. 
Only by examining for several well-defined constants, 
can any useful estimate of the general fitness of the 
glue be formed. 

Accordingly, the dry glue must be examined as to 
color, finish and odor, and, if in the form of flake, 
sheet, ribbon or strip, as to the nature of the fracture 
when a piece is broken between the fingers or by other 
means. The solution must be examined as to odor, 
acidity or alkalinity, grease, foam and viscosity. The 
jelly resultant from the solution is tested for strength. 
The viscosity and jelly strength are compared with 
those of accepted standards. 

Standards. — The constants or measurements of 
quality in glue-testing are arbitrary and of value only 
when compared with the corresponding constants of a 
standard glue. The consumer is frequently at a loss 
to select the proper standards of comparison. He is 
usually content, having secured a glue that fully 
answers his requirements, to compare each succeeding 
delivery with this. While this doubtless enables him 
to check uniformity of delivery, it in no wise answers 
the question with which he is chiefly concerned; namely, 
was the original purchase which he now uses for a stand- 
ard, the best quality obtainable for the price paid? To 
possess this degree of protection, he must adopt the 
identical standards employed by the manufacturer in 
assigning price. 

Manufacturers avail themselves of the Cooper grades 
as standards of comparison. These are eleven in num- 
ber, and proceeding from STRONGEST TO WEAKEST, are 
_ designated: 


22 GLUES AND GELATINE 


A Extra. 

1 Extra. 

No. 1. 

1 X (“one cross’’). 

14 (“fone and a quarter’’). 

13 (“one and three eighths’’). 
4 (“one and a half’’). 

18 (“one and five eighths’’). 

12 (“one and three quarters’’). 

1% (“one and seven eighths’’). 

No. 2. 


These grades were for many years considered the best 
made, and competing manufacturers sought to produce 
glues corresponding with them in all respects. Hence 
they remain the authentic standards of comparison. It 
must not be inferred that they are the only reliable 
make of glue. Many manufacturers produce glues far 
stronger than the A Extra, and the other grades are 
regularly duplicated. 7 

It will be readily understood that glues are produced 
which, in strength, fall between the various grades. 
No manufacturer is so expert that he can proceed with 
the definite intention of producing a glue of A Extra or 
12 or No. 2 strength. He can control the strength of 
the product only by the careful selection of stock and 
in the treatment throughout the course of manufacture, 
as outlined in the previous chapter. Once finished, the 
glue must be compared with the above standard grades 
in order that it may be classified and a price assigned 
to it. Hence the value of their employment by the 
consumer, if he desires to be enlightened upon the all- 
important factor of price. Furthermore, the peculiar 
designations of these grades have become the accepted 
vernacular of the trade. While defying definition, the 


CLASSIFICATION AND TESTING OF GLUES — 23 


term 13, for example, conveys to the initiated not only 
the idea of definite strength, but also enables him to 
form a definite estimate of the limits of price. In addi- 
tion, the acceptance of the Cooper grades as standards 
is justified by their unfailing uniformity. While the 
manufacturers are subject to the same limitations as 
_ others in attempting to predetermine the strength of 
their glues, with the result that they produce many 
that fall between the various grades, these latter do not 
come into the market under the manufacturer’s name, 
only those that are up to standard in all particulars 
receiving their special brand. The result is, that the 
14 of to-day is identical with that of five years ago. 

Test Methods. — The dry glue should first be carefully 
examined, for, while the appearance of the glue, save 
in isolated instances, tells nothing in regard to its 
strength, such examination is often sufficient to warrant 
the rejection of the glue, without the necessity of further 
tests. The following points are worthy of considera- 
tion: 

1. The surface of the piece of glue should be free 
from bubbles. These may be merely the result of the 
incorporation of some air with the glue; but, if sizeable 
and irregular in outline, they are evidence of the fact 
that the stock from which the glue was made, and 
hence the glue itself, is in an advanced stage of decom- 
position. Of such a glue, the jelly will rapidly putrefy 
and the solution will have a putrid odor, which, in some 
instances, may be detected in the glue itself, particularly 
if the sample be slightly moistened. 

2. The piece of glue should break with an even 
fracture. If the fractured edges are splintery, the glue 


24 GLUES AND GELATINE 


has not been properly boiled. On the other hand, if a 
glue breaks under a very slight strain, even though the 
fracture be even, the glue is either very weak or unduly 
dry. 

3. A good glue should present a velvety or glossy 
surface, although the absence of this does not always 
condemn the glue. A “dead” surface may be due 
merely to the fact that dust settled upon the glue while 
it was drying upon the nets. 

4, The cut of the glue is at times an indication of its 
strength. If, for example, the glue is cut very thin 
and is sufficiently flexible to permit of bending almost 
double without fracture, it is a glue of great strength. 

5. If the sample is a flake glue, it is well to compare 
several pieces in a good light, for even flake glues may 
be mixed. They are somewhat difficult of recognition 
inasmuch as the dealer is at great pains in selecting the 
constituents of such mixtures. Mixed ground glues are, 
of course, frequently met with. Such as are a mixture 
of foreign and domestic grades may readily be recog- 
nized with the aid of a magnifying glass; the particles 
of the foreign glue being usually lighter in color and 
more transparent than the domestic. Mixtures of two 
or more foreign grades may be detected by noting the 
differences in color exhibited by the particles. In exam- 
ining ground glues to detect mixture, the observer must 
not be led astray by slight differences in color, as in all 
eround glues some particles are finer than others, and 
hence lighter in shade. 

Sampling. — The sampling of the glue preliminary to 
test is of the greatest importance. The small sample 
of a few ounces which is usually submitted to the 


CLASSIFICATION AND TESTING OF GLUES 25 


prospective purchaser should be the subject of the 
above preliminary examination. If it is a flake glue 
and is seen to be a mixture, a little of each constituent 
must be taken for test. Where the dealer goes to the 
extreme of mixing flake glues, he uses a strong glue as 
a base, and adds enough of a weaker and hence cheaper 
glue to make the price right. Hence, unless the above 
precaution is observed in connection with the sampling 
of a mixed flake, the result of the test is misleading, 
as the operator may unwittingly select pieces of the 
stronger glue only, or portions of the weaker alone. 
It is rare to find more than two constituents in a flake 
mixture, whereas, with ground glues, as many as four 
different grades may be mixed together. If the initial 
sample is a ground glue, even though the preliminary 
examination reveal no mixture, it 1s well to shake the 
package thoroughly before withdrawing the quantity 
required for test. In the case of mixed ground glues, 
this precaution must invariably be observed. 

_ Many consumers are content with an examination of 
the sample and take for granted that the delivery will 
correspond with it. Such render themselves an easy 
prey to the unscrupulous dealer. It is manifest that if 
the consumer is to achieve the full measure of protec- 
tion, he must test the delivery and note wherein this 
differs, if at all, from the original sample. Having, 
furthermore, secured a delivery to his entire satisfaction, 
he should reserve a generous portion to be used in 
conjunction with the other standards in future tests. 
Whether the delivery consist of a single barrel or a 
ear-load, the sampling should be done systematically. 
Glue is sometimes stored in a damp place that addi- 


26 GLUES AND GELATINE 


tional weight may accrue to the barrel. In such case, 
those portions contiguous to the top and the bottom 
of the barrel contain more moisture than that at the 
center. Hence, if the glue is ground, even though the 
preliminary examination does not show it to be a 
mixture, samples should be withdrawn from several 
parts of the barrel, including the center, and should 
then be mixed well together and the requisite test- 
quantity withdrawn from this. This applies equally 
to flake glues, when the several samples should be 
comminuted in a small mill and, after mixing the ground 
resultant, the test sample may be weighed off. 

Where the test is concerned with a bundle of gelatine, 
it does not suffice to select only one sheet from the 
bundle, but small pieces of each sheet should be broken 
off; and. where there are a number of bundles, samples 
selected in this way should be taken from each. 

It may be objected that this sampling consumes too 
much time. Nevertheless, if the test is to be represen- 
tative of the delivery, the above precautions must be 
observed in detail. The writer has been frequently 
called upon to test a car of glue (sixty barrels), of 
which no two tested exactly alike. The operator is, 
of course, at liberty to adopt such methods of sampling 
as will expedite the test; but he must be sure that the 
sample he tests is an average one, else the whole test is 
a waste of time. It will save time if, when the glue to 
be tested is in the flake, the sample be ground prior to 
soaking. The writer successfully employs for this pur- 
pose a small coffee-mill in which the sample may be 
ground to varying degrees of fineness. This prelimi- 
nary grinding of flakes often aids in the development 


CLASSIFICATION AND TESTING OF GLUES 27 


of hidden odors. Inferior grades of glue may betray 
no undue odor when in the dry piece, but, when freshly 
ground, these become manifest and are subsequently 
verified in the solution of the glue. 

Before describing the test system as a whole, we shall 
review the methods applicable to the determination of 
the individual factors. ' 

1. Odor of the Glue Solution. — The glue having been 
dissolved to a solution of definite strength (see below), 
any odors emanating from the hot solution should be 
noted. The solution should be ‘‘sweet.’”’ This does | 
not mean that it should be free from any odor whatso- 
ever, aS even the solution of the purest gelatine will 
have a characteristic smell. There should be no trace 
of putrefaction. If the glue is very greasy, this may 
impart an odor to the solution, and yet the glue be: 
rated sweet. The odor of the solution will vary accord- . 
ing to the stock from which the glue is made. Thus, 
solutions of common bone glues have a marked “ beefy” 
or “soupy” odor, and yet may be excellent glues of 
their class. Goat and sheep stocks impart a charac- 
teristic odor to the glues prepared from them, while 
glues from skin or epidermis are more or less odorifer- 
ous. 

It is difficult to describe an “off” odor in glue, but 
this requires no extended experience to recognize. — 
Frequently a glue that exhibits a disagreeable odor 
upon going into solution loses this completely as the 
solution becomes hotter. Care must be taken not to 
condemn the glue because of smell, without first con- 
sidering whether this be not due only to the stock. 
Odors due to partial putrefaction and other radical 


28 GLUES AND GELATINE 


defects are permanent, and heating the solution does 
not dissipate them. Acid-treated glues, particularly 
those from junk bone, are, as a rule, very sweet, though 
some smell strongly of acid. 

2. Alkalinity and Acidity. — Few glues are strictly 
neutral when in solution, being either acid or alkaline, 
depending upon the treatment which the stock has 
received. As previously stated, some manufacturers, 
after liming the stock, kill the excess of lime by means 
of a mineral acid. Glues boiled from such stock will 
be more or less acid in reaction, as will also those pre- 
pared by leaching. Where the bulk of the lime has 
been removed from the stock by simple washing, enough 
remains to impart to the solution of the finished glue an 
alkaline reaction. 

Sufficient acid or alkali is present to react with litmus, 
-and hence either condition is conveniently determined 
by dipping, first, a strip of blue litmus paper into the 
hot solution, and subsequently a strip of red litmus 
paper. If the glue is acid, the blue litmus strip will be 
more or less reddened and the red strip unaffected; 
conversely, if alkali is present, the blue strip will be 
unaffected while the red strip acquires a blue coloration 
varying in intensity with the amount of alkali. The 
test is best carried out by immersing the dry strips 
in the hot glue solution and, after keeping about one 
half the strip submerged for thirty seconds, withdrawing 
and draining the excess of glue solution by wiping both 
sides of the strip on the edge of the vessel containing 
the solution. If too much extraneous solution be per- 
mitted to adhere to the strip, it is difficult to observe 
the change of color. 


CLASSIFICATION AND TESTING OF GLUES 29 


Excess of acid or alkali in glue is of disadvantage 
chiefly where the glue is to be employed in sizing deli- 
cate colors, or insoluble lake pigments (‘‘pulp colors’’), 
as in the wall paper and surface-coated paper industries. 
Many of these pulp colors, particularly the cheaper 
grades, are poorly fabricated, the excess of material 
employed to precipitate the aniline or coal-tar color 
upon the insoluble base having been only partially 
washed out. As a result, trouble frequently arises in 
the wall paper factory, owing to the inter-reaction of 
the acid or alkali in the glue and the excess of pre- 
cipitant in the colors. In the same industry, difficulty 
is at times experienced owing to lack of smoothness in 
the mixture of glue and clay used for the initial grounds. 
Excess of acid or alkali in the glue employed for sizing 
the clay often has a disintegrating effect upon it, the 
mixed clay and glue solution becoming lumpy and 
leaving the rollers of the machine in irregular patches 
instead of with a uniform flow. 

Unless acid or alkali is present in large excess, it may 
be disregarded save as indicating, to a certain extent, 
the treatment which the stock has undergone. It has 
already been noted that acid glues keep longer than 
alkaline ones, as the bacteria of decomposition repro- 
duce far quicker in alkaline media than in acid. If the 
glue has a rather earthy smell, and the solution turns 
red litmus deep blue, the stock has been over-limed. 
Such a glue should be rejected as the excess of alkali in 
this case will gradually weaken the glue, causing it to 
rot rapidly. Although the appearance of over-limed 
glue may frequently give indication of strength, upon 


30 GLUES AND GELATINE 


pated, owing to the fact that the lime has already 
radically weakened the fiber of the glue. 

3. Grease.— The presence of grease in glue has 
always met with strenuous objection, more or less 
justified, upon the part of the consumer. As a matter 
of fact, its presence is of material advantage for some 
purposes and of equal disadvantage for others. In any 
one make of glue, the amount of grease will vary con- 
siderably in the course of, say, a year. As has been 
pointed out, there are times when the manufacturer 
relies upon the recovery of the bulk of grease in order 
to reduce the cost of production. At others, when the 
market value of the recovered and rendered grease is 
so low as not to warrant the additional labor-cost 
attendant upon its complete removal, he permits a 
goodly proportion to remain in the liquors, and this is 
subsequently detected in the finished product. 

A simple and accurate test for grease is effected by 
placing upon the corner of a sheet of white paper a 
few grains of some aniline color such as methyl violet, 
magenta, or any other readily soluble in water. A clean 
flat brush, one or two inches in width, the edge evenly 
trimmed, is dipped in the glue solution, which must be 
hot (170-180° F.) so as to insure a good flow of the 
solution, which is apt to cool rapidly upon the surface 
of the paper. The brush is withdrawn from the solu- 
tion, hastily drained, and then applied to the color 
with a stirring motion so as to dissolve all. Without 
lifting the brush from the surface of the color, it is 
drawn with a rapid sweep across the paper. Any 
grease will manifest itself in the form of ‘‘eyes” or 
elliptical spots which soon disappear. Bubbles of air, 


CLASSIFICATION AND TESTING OF GLUES 31 


arising from faulty manipulation of the brush, must 
not be mistaken for grease spots. The more color 
used, the better the grease will show. Excellent results 
may be obtained by keeping the brush always firmly 
pressed against the surface of the paper in dissolving 
the color as well as in the subsequent ‘painting out.” 
The best results of all can be had by using lampblack 
in place of aniline color; but this has the disadvantage 
of being insoluble in water and hence it is difficult to 
clean the brush properly for the next test. 

Glue at times contains free fatty acids resulting from 
the destruction of lime soaps by mineral acids. These 
impart a more or less acryline odor to the hot solution. 
Their presence is sufficient to condemn the glue, as they 
are markedly hygroscopic, absorbing sufficient atmos- 
pheric moisture to radically retard drying of the solu- 
tion. | 

Of the various glues, that made from sheep stock is 
the greasiest. Next in order comes glue made from 
goat; and glues from ox or cow hides are more or less 
greasy, depending upon the care exercised in the re- 
moval of fat. Acid-treated glues seldom exhibit more 
than a trace of grease. 

In the manufacture of ‘‘glazed”’ or surface-coated 
papers, greasy glue is undesirable, for reasons that are 
manifest. Since the glue is incorporated as a size or 
binding medium with the colors, any grease would show 
upon the surface of the paper just as in the test. For 
similar reasons, greasy glue is regarded unfavorably by 
the manufacturer of wall papers. It is claimed that 
the grease is apt to penetrate the paper, making typical 
grease spots. The objection is not a good one; as the 


32 GLUES AND GELATINE 


formation of such spots would presuppose the presence 
of an enormous excess of grease to penetrate both paper 
and clay ground. On the contrary, the presence of 
even a moderate amount of grease is of advantage. 
It not only prevents the glue from foaming in connec- 
tion with the clay or colors, but serves to materially 
brighten the latter even though it may somewhat re- 
tard the drying of the printed paper. In the majority 
of instances where the glue solution is applied to the 
material to be sized by means of a machine roller, the 
presence of a small amount of grease assists, rather than 
hampers, the operation, preventing foam and insuring 
smoothness of flow from the roller. 

4, Viscosity. — As applied to solutions of glue and 
gelatine, the term viscosity comprehends their rate of 
flow as compared with that of a standard fluid, viz., 
water. Just as two solids, two blocks of wood, for 
example, moving against each other, exhibit more or 
less friction or resistance to movement, according as 
their surfaces are smooth or rough, so do fluids manifest 
friction or resistance to movement, not only towards 
the solid surfaces over which they flow, but also between 
their constituent molecules. Viscosity has its origin in 
the ease, greater or less, with which these molecules pass 
or roll over one another. It is exhibited by all liquids 
to a varying degree. If a vessel of water be given a 
slightly rotary.motion, so as to cause its contents to 
oscillate, it will be observed that with each swing the 
amplitude of the oscillation becomes smaller, the oscil- 
lation gradually ceasing and the surface of the liquid 
coming to rest. If oil or glycerine be substituted for 
the water, and the experiment repeated, a much greater 


CLASSIFICATION AND TESTING OF GLUES ~ 33 


resistance to movement will be observed, due to the 
viscosity or internal friction of the fluids. 

The measure of the viscosity of the glue solution is 
important. It has been adopted by several prominent 
Western manufactories as the sole means of determining 
glue strength. Of itself, it is insufficient for this pur- 
pose, but, considered in conjunction with jelly strength, 
it is of great value in grading the glue. It is an arbi- 
trary constant and is of value only when compared 
with the corresponding measure of a standard fluid. 
Thus, to say that the viscosity of a glue solution is 
35 seconds conveys absolutely no meaning; but from 
the statement that the viscosity is 35 seconds, when, 
under the identical conditions, the viscosity of water 
is 15 seconds, a definite estimate of the ““body” or rate 
of flow of the glue solution, can be formed. Water is 
advisedly the standard of comparison for viscosity, 
since it is the medium for extracting the glue stock, 
and the strength of the glue is in large measure depend- 
ent upon the amount of gluey material that has com- 
bined chemically with the water. It must not be 
inferred from this that the higher the viscosity, the 
stronger the gluc. This is true only of certain kinds 
of glue. 

Owing to the importance of determining the viscosi- 
ties of lubricating oils, several elaborate forms of 
viscosimeter have been devised, such as the Engler, 
Sayboldt, Hurst, Coleman-Archbutt, Kunkler and Red- 
wood. These may be employed in the determination 
of the viscosities of glue solutions; but they supply 
figures that are inconveniently high and have, further- 
more, been standardized by means of oil and not water. 


34 GLUES AND GELATINE 


Satisfactory results can be obtained with much simpler 
apparatus. 

The simplest form of viscosimeter consists of a 
volumetric pipette, of about fifty cubic centimeters 
capacity. This is shown at Fig. 1. By means of a 
q file, the delivery end is cut off at a 

and the aperture carefully reduced 

in the Bunsen flame, the object being 
to procure an instrument that will 
deliver water from the mark b to the 
» aperture c in exactly 15 seconds, 
\ measured by a stop-wateh. Any re- 
liable dealer in chemical apparatus 
will, at low cost, make such a pipette. 

Should the operator himself desire to 

standardize the instrument, he pro- 

ceeds as follows. Having shortened 
the delivery tube as directed, the 
aperture is first shghtly reduced by 

holding it in the flame, giving it a 

rotary motion so as to preserve the 

circular perimeter. A trial had best 
first be made with a piece of glass 
tubing, in order that the necessary 
precautions may be studied. The 
aperture is at first only slightly reduced, when, having 
cooled, the pipette is filled and adjusted to the mark b. 
In filling a pipette, it is held by the upper tube bd be- 
tween the thumb and middle finger of the right hand, 
leaving the index finger free to be placed subsequently 
at d. The point c is immersed in the liquid and the 
lips applied at d, the liquid being drawn by gentle suc- 


FIG. 1 





CLASSIFICATION AND TESTING OF GLUES 35 


tion to some point between b and d. As the lips are 
withdrawn, the index finger is instantly placed at d and 
pressed firmly against the tube-end so as to maintain 
the level of the liquid. By gently releasing the pres- 
sure of the finger, the liquid will flow to b and is held 
at this point by firm pressure of the finger. The 
operator now takes the stop-watch in his left hand, 
using the thumb to release the movement of the watch. 
With the pressing of the spring, he simultaneously re- 
leases the contents of the pipette by removing his 
finger, and as the last drop of the contents passes c he 
closes the movement of the watch. The time required 
for the contents (water, free from sediment, at about 
180° F., is used for the standardization) to flow from b 
to cis registered by the watch. If the operator has pro- 
ceeded carefully, this will be 12 or 13 seconds on the 
first trial. 

It is now necessary to close the aperture c still 
more. The pipette is thoroughly dried (carelessness in 
drying will inevitably result in the breaking of the 
instrument) and the point cis held in the flame with 
the usual rotary motion until it just reddens. Care 
must: be taken not to close the aperture too far as 
otherwise the point must be broken and the entire 
operation begun over again. Having cooled, the pi- 
-pette is filled and adjusted as before, and the time of 
delivery again noted. On this trial it will be found to 
be nearly correct — about 145 seconds. The greatest 
care must now be exercised in so adjusting the aperture 
that the time of delivery will be exactly 15 seconds. 
The pipette is again dried and the point c held in the 
flame a few seconds only at a time, repeated trials of 


36 GLUES AND GELATINE 


delivery being made between heatings. When the time 
of delivery between the points 6 and c¢ is exactly 15 
seconds, the instrument is ready for use. 

Much labor may be saved by the inexperienced oper- 
ator, if he will first study the principles of manipulation 
by using a piece of glass tubing. In this way he will 
be able to see just what is necessary in properly reducing 
the aperture of the pipette. The selection of a pipette 
of 50 c. ce. capacity supplies figures that are most con- 
venient in use. The time of delivery is purely arbitrary, 
and may be any larger figure than 15 seconds. ‘This, 
however, is the most convenient. Pipettes of larger 
capacity, supplying larger figures for viscosity, are awk- 
ward to handle and the contents cool perceptibly during 
efflux, the resulting figures being inexact. By the 
system recommended, it will be found that the lowest 
viscosity exhibited by a 25 per cent glue solution is 
154 seconds, or one half second greater than that of 
water under the same conditions; while the highest will 
rarely exceed 70. 

An improved form of viscosimeter is shown at Fig. 2. 
The instrument is of 50 ¢. c. capacity and is provided 
with a glass stop-cock s, which obviates the necessity 
of controlling the contents with the finger as in the 
above form. The points of flow are a, the lower 
surface of the stop-cock, and the aperture c. ‘The 
instrument is standardized in the same way as the 
plain pipette. After filling with the glue solution and > 
adjusting to the mark, the upper tube is firmly clamped 
to a support, leaving the operator free to release the © 
watch movement and open the cock simultaneously. 

Where great accuracy in the determination of the 


CLASSIFICATION AND TESTING OF GLUES 37 


viscosity is desired, the following form of viscosimeter, 
devised by the author and used by him throughout his 
tests, will be found to give satisfactory results. The 
instrument is shown at Figs. 3 and 3a. It consists of 
the viscosity pipette, A, and the bath B for maintaining 
the contents of the pipette at con- 

stant temperature. ‘The pipette is 

provided with the stop-cock S for 

controlling the contents, and the 

time required for the contents to 

flow from x to cis exactly 15 sec- - 

onds. 

The bath B is made of seamless 
copper and consists of an outer 
compartment D which serves as a 
water-jacket, and an inner cylinder 
in which the pipette A snugly fits. 

This cylinder projects some dis- % 

tance below the jacket D, and is 
provided with a window, F’, made 
of thin sheet mica, so that the 
aperture of the pipette may be 
clearly seen. 

At Fig. 3a the apparatus is seen set up and ready 
for use. The bath B is supported by the ring G of the 
ring-stand. Some distance below is adjusted the ring- 
burner EL, by which the water in D is brought to the 
desired temperature recorded by the thermometer 7’. 
The pipette is shown snugly fitting in the inner 
cylinder, ready to discharge the glue solution, y. The 
aperture c of the pipette is visible through the win- 
dow F. The contents of the pipette are returned 


FIG, 2 


38 GLUES AND GELATINE 


to the glass, H, in which the glue was originally dis. 
solved. 

The pipette having been filled and the contents ad- 
justed to the mark, it is placed in the cylinder and the 





ie 
FIG. 3a 





water in D brought to about 185° F., making the tem- 
perature of the contents of A practically 180° F. Sim- 
ultaneous with the release of the contents, effected by 
giving the stop-cock a sharp turn, the watch, held in 


CLASSIFICATION AND TESTING OF GLUES 39 


the left hand, is started, and the moment the last drop 
has passed c the watch is snapped and the time of 
efflux between x and c noted. This is the viscosity of 
the glue solution, as compared with water, standard = 
15. The viscosity may also be expressed in terms of - 
water as unity, by dividing the number of seconds for 
the glue solution by 15. Thus, if the glue solution has 
a viscosity of 27 seconds, this may also be expressed 
as 1.80 referred to water as unity. 

Certain precautions are to be observed in taking the 
viscosity. All the glues to be compared must be at 
exactly the same temperature (180° F.). Furthermore, 
they must be of exactly the same strength. Itis obvious 
that two solutions of the same glue, one 10 and the 
other 25 per cent, will exhibit widely divergent 
viscosities. During the test, the temperature of the 
_ glue solutions should not exceed 180° F., as the pro- 
tracted heating is apt to decrease the jelly strength. 
Again, the operator must practise until he is able to 
release the contents of the pipette and start the stop- 
watch simultaneously. He must keep his eye constantly 
directed to the point c that he may be prepared to snap 
the watch the instant the last drop passes that point. 
Practice for a short time will enable him to execute the 
test with absolute accuracy. 

Value of Viscosity as a Test Factor. — By some, 
notably Western, producers, viscosity is taken as the 
ultimate measure of glue strength. This is a grave 
error. Viscosity is of importance in the glue test as it 
indicates the treatment the stock has undergone; and 
is, further, a reliable index of the value of the glue as 
a sizing medium. It must, however, be considered side 


40 GLUES AND GELATINE 


by side with other factors. The assumption that the 
strength of the glue is in direct ratio to the viscosity 
of its solution is true only of certain glues. Those 
prepared from the same stock, under identical condi- 
. tions, may exhibit viscosities varying directly as their 
strength; but these constitute the exception rather than 
the rule. The fallacy of rating glues according to 


viscosity alone, will be readily seen from consideration. 


of the following. It is assumed throughout that the 
glues are in 25 per cent solution, and that their viscos- 
ities at 180° F. are referred to water = 15 seconds. 

The viscosities of the Cooper grades seldom vary and 
then only by a few seconds, the average being: 


AUEIXUr6 (|. as eu | ee 45 seconds. 
t. Mixtral ose 5.4 ER OR ee 40 2:5 
NO] Auk do i a ee 35 * 
1 X molding (opaque)........... Ain gta mee 
1X, clear 025 Vn. eds. a pe 29 & 
14g eS Eee eee eee PY Saat 
13 ones ebtacd ye es Oe 25 32 
oe Si rae: 
1 eee RN Py eee 
We ee ee 193 « 
1} a ayia SN ae IS se% 
NO, 205. as Pine ed wegen ee 164-57 


It will be observed that the higher grades exhibit 
greater divergence in viscosity than the lower. Such is 
the case with the majority of glues. 

Assume, now, that the above are being employed 
as standards, and that the operator relies solely upon 
the viscosity as the ultimate measure of the glues he is 
testing. Of four glues on test, he finds, let us say, the 
viscosities to be 35, 26, 22 and 19 seconds, respectively. 
His inference is that the first tests No. 1, the second 


CLASSIFICATION AND TESTING OF GLUES 41 


1}, the third 14, and the fourth 13. If the glues he is 
testing were made from the same stock and under the 
same conditions as those in the above table, his infer- 
ence would be correct; but unless such were the case, 
his report would be entirely wrong. 

Acid-treated bone glues, as well as those from acid- 
treated hide stock, exhibit viscosities remarkably low 
in proportion to their jelly strength. Such glues, of 
A Extra strength, may have as low a viscosity as 30 
seconds, and acid-treated glues of 12 strength, with 
viscosity as low as 18 seconds, are common. Hence, 
had any of the above glues on test been derived from 
acid-treated stock, for example, the one with viscosity 
of 19 seconds, its jelly strength might be 1 X and not 
12. Now, suppose this glue had been offered at 10 cents 
per pound. The operator, rating it as a 1? glue, would 
at once have decided that the price was ridiculously 
high; whereas, had he rated it properly as 1 X, he would 
have realized that he was offered a bargain. 

The viscosities of opaque and colored glues are 
always slightly higher than those of clear glues of 
corresponding strength (compare 1 X molding with 1 X 
clear in the above table of standards). Hence, if vis- 
cosity is to be taken as the ultimate measure of strength, 
it is necessary to provide separate standards for com- 
paring opaque or colored glues, separate standards for 
clear glues, for hide glues, for bone glues, and for acid- 
treated glues. Even if this were done, the results 
would not always be accurate, as will be understood 
from the following considerations. 

If the glue stock has been incompletely washed, per- 
mitting mucin to be present, or if it has been over- 


42 GLUES AND GELATINE 


limed, with the result that soaps are present in the 
finished article, the viscosity will be disproportionately 
high. The author has seen glues which, while testing 
only 1%, have had as high a viscosity as 30 seconds. 
Others, testing A Extra, had viscosities ranging from 
59 to 69 seconds. These were hide glues from improp- 
erly washed or over-limed stock. 

The majority of foreign glues, and certain grades of 
domestic, having been clarified, are low in viscosity. 
This applies to both bone and hide glues. If the 
clarification has been effected by means of alum, the 
viscosity is very high, as alum renders the glue solution 
stringy. This is to be observed in the case of rabbit 
glues, the viscosities of which would mislead the observer 
as to their strength. Gelatines, because of the special 
stock from which they are made, and the special treat- 
ment which this undergoes, are comparatively low in 
viscosity. 

Table I, compiled from the author’s laboratory note- 
book, will convey some idea of the variation in viscosity 
shown by gelatine, hide glue, acid-treated and regular 
bone glues, of the same Jelly strength. 

Table IIT emphasizes the fallacy of relying solely upon 
viscosity in rating the glue. It is seen that the gela- 
tine with a viscosity of 49 seconds is two grades stronger 
than the hide glue with the same viscosity. Similar 
discrepancies are to be noted throughout. 

The manufacturer who manipulates constantly the 
same stock and whose processes are never altered, 
might use viscosity alone to rate his product, provided 
that the standards of comparison were his own glues. 
He would first have to compare these with the accepted 


CLASSIFICATION AND TESTING OF GLUES 48 
TABLE I 


GLUE SOLUTION = 25 Grams IN 100 c. c. WATER. 


VISCOSITY VISCOSITY 
OF THE pease OF THE 
AciD-TREATED REGULAR 
GELATINE 
BONE GLUE BoNE GLUE 


VISCOSITY 
OF THE 
HipE GLUE 


JELLY 
STRENGTH 


seconds seconds 
seconds seconds 
seconds seconds seconds 
seconds seconds seconds 


seconds seconds seconds 
seconds seconds seconds 
seconds seconds | 174 seconds 
seconds seconds 21 seconds 
194 seconds 19 seconds 
184 seconds 18 seconds 
17 seconds 16 seconds 








TABLE II 


TaBLE, SHowinc Trests or Bone, Actp-T'reatep Bons, Hips 
GLUES AND GELATINE, CORRESPONDING TO 
A CERTAIN VISCOSITY: 





WHEN THE THE TEST THE TEST Tre Teer or THE TEST OF 
VISCOSITY OF THE OF THE ACID- G THE REGULAR 
OF THE Hive Give | TReatep Bone| TE VELATINE BONE GLUE 
: SOLUTION Is MAY BE GLUE MAY BE MAY 3% MAY BE 
a0-seconds | A Wxtra' |.....2...... FA ATIAS HCP eh) Se ctr eee 
apeepeonds | A’ Extra |............ SANS Fobra hata Geided ge 
40 seconds La OVS ec a ACS race 2° ele! Bere 
35 seconds 1 Extra (AS Soxtrs wie fee oto 
31 seconds No. 1 tExira: Piero ee 
27 seconds i Sew, @ No. 1 SON bo oe Ae 
24 seconds 14 1B COL cave me nae 
22 seconds 13 fen eee at 
20 seconds 14 13 13 
18 seconds 13 14 1Z 
16 seconds 13 18 No. 2 





1 From over-limed stock. 2 Strongly alkaline. 


44 GLUES AND GELATINE 


standards, else, outside his own establishment, his grades 
would be meaningless. 

The exact value of viscosity as a test factor will be 
better understood after the reader has studied the 
discussion of the test system as a whole, in the suc- 
ceeding pages. 

5. Foam. — Foam, in glue, arises from the incorpo- 
ration of minute bubbles of air with the solution, when 
this is beaten rapidly. There may be present in the 
solution, substances which render the emulsion more or 
less permanent; or the emulsion may be only tempo- ° 
rary, the foam receding and disappearing in a few 
moments. The same defects which fictitiously increase 
the viscosity, contribute materially to the foam in glue. 
Thus, over-limed or poorly washed stock will retain 
mucin or soaps which make the solution foam badly. 
Glues from alum-clarified liquors foam, as do also cheap 
bone glues, because of the impurities they contain. If, 
however, there is grease present to any extent, it will 
prevent the foam emulsion from forming. This applies 
to all makes of glue. 

Foam, although undesirable in glues, is often de- 
manded in gelatine, particularly that used for the 
manufacture of confectionery. In making marshmal- 
lows, the solution of gelatine, combined with other 
ingredients, is beaten rapidly in a special machine. 

_ The test for foam is executed as follows: 

The hot solution previously employed for the odor, 
crease and viscosity tests is transferred to a stout 
glass vessel, wide enough to accommodate the usual size 
of rotary egg-beater. This vessel should be neither so 
thick that the heat of the solution will crack it, nor 


CLASSIFICATION AND TESTING OF GLUES 45 


yet so thin that it is apt to be broken by the egg-beater. 
On the side, a mark should be placed at the level of 
the glue solution, and above this three others, a half 
inch apart. The egg-beater is slowly rotated in the 
solution for half a minute and the quality as well as 
the quantity of foam noted. If this is only slight and 
disappears in a moment, the glue is non-foaming; if 
somewhat more permanent and reaching the second 
line, the glue is slightly foamy. If the column of foam 
reaches the third mark and takes some time to recede, 
it is moderately foamy; and soon. The operator should 
agitate the solution neither too rapidly nor too long, as, 
under these conditions, any glue solution will emulsify. 
The test conditions should be approximated to those 
obtaining in actual work. Two revolutions of the egg- 
beater, per second, will suffice for the test. 

6. Jelly Strength. — This is the most important of 
all the test factors and, unless considered in conjunction 
with this, the others are of only limited value. The 
stronger a glue, the greater the resistance offered by 
its jelly to outside pressure. The statement that a 
glue tests 14 means that its jelly offers the same degree 
of resistance to pressure as the Jelly of the standard 

4 olue. Test methods seek to measure this resistance 
in definite terms. 

So many divergent methods for determining glue 
strength have been formulated, that lack of space 
forbids their discussion here. Those dependent upon — 
chemical operations are absolutely worthless, as has 
already been noted. Those involving the use of special 
apparatus supply results that in no way. correspond 
with the commercial value of the glue. Of these, the 


46 GLUES AND GELATINE 


test with the so-called “shot machine” is worthy of 
some notice, although the method is open to considerable 
criticism. | 
The shot test was formulated by Lipowitz, whose 
apparatus, shown at Fig. 4, has since received con- 
siderable modification. The 
test has for its object the de- 
termination of the weight 
sustained by the glue jelly. 
Upon the surface of the jelly 
rests a saucer-shaped piece of 
tin. The iron rod connecting 
—— this with the funnel designed 
) Hin 7 to hold the shot passes 
Up through and is supported by 
af | the tin cap which rests upon 
the edges of the glass contain- 
ing the jelly. The combined 
weight of the saucer, rod and 
funnel does not exceed half 
an ounce. Into the funnel, 
shot is poured until the saucer 
just penetrates the jelly. The 
































































shot is then weighed. 

It will be seen that no account is taken of the friction 
between the parts of the apparatus, as well as that 
between the saucer and the jelly. This objection holds. 
better with the more modern forms of shot apparatus 
in which the rod is permitted to sink through the entire 
jelly and rest upon the bottom of the glass. Again, 
the formation of a skin on the surface of the jelly 
frequently invalidates the test, as the weight deter- 


CLASSIFICATION AND TESTING OF GLUES 47 


mined is really that required to pierce this skin and 
the jelly, plus that required to overcome the friction 
between the penetrating rod and the skin and jelly. 
Lipowitz’s apparatus is undoubtedly the best form as 
it is required just to penetrate the surface of the jelly. 
For certain classes of glues it is a fairly accurate test. 
In practice, however, the comparison, by its means of 
a clear glue and an opaque of identical strength, yields 
divergent results, as the skin on the opaque glue is 
slightly tougher than that on the clear. 

For practical commercial purposes, there is no better 
method of measuring the resistance of the glue jelly 
than by means of the finger. The fourth finger of the 
left hand is used, as it is the most sensitive of all. In 
operation, the test is as follows: 

The glues, having jelled, are arranged in a single fife 
on the table before the operator. Let us assume that 
these are nine in number, five unknown glues and four 
standards, the latter being 14, 13, 1? and No. 2. The 
glues are in numbered glasses, the unknown being 
numbers 1, 2, 3, 4 and 5; and the standards, numbers 
6, 7, 8 and 9. They are arranged in numerical order, 
running from left to right. The operator first assigns a 
preliminary rating. To effect this, he first presses the 
finger upon the jelly of No. 1 and then on that of No. 2. 
Any difference in the resistance of the jellies to the 
pressure of the finger is at once noted. If No. 2 offers 
less resistance than No. 1, the glasses remain as they 
are; but if it is seen that No. 2 is the stronger, it is 
shifted to the left of No. 1. If the order of the glasses 
remains unchanged, the operator next compares Nos. 2 
and 3; but, if 1 and 2 have changed places, he compares 


48 GLUES AND GELATINE 


1 and 3, the stronger jelly always being placed to the 
left of the weaker, and so down the line. . In this way 
the glasses are finally so arranged that the strongest 
jelly of all is at the operator’s extreme left and the 
weakest at his right, the intermediate glasses repre- 
senting successive steps in strength, calculating from 
right to left. 

In the hypothetical case under discussion, we shall 
assume that, at the end of the preliminary rating, the 
glasses stood as follows, proceeding from left to right: 


No. 5, No. 6, No. 4, No. 7, No. 3, No. 2, No. 8, No. 1, No. 9. 


The operator now compares No. 5 and No. 6. He 
finds, let us say, that these are equal in strength, as 
they offer exactly the same degree of resistance to the 
pressure of his finger. Comparing Nos. 6, 4 and 7, he 
finds that No. 4 is weaker than No. 6 and yet stronger 
than No. 7, appearing to be exactly half-way between 
the two. In the same way he finds that No. 3 is half- 
way between No. 7 and No. 8; that Nos. 2 and 8 are 
of equal strength, as are also Nos. 1 and 9. Upon con- 
sulting the list of standards suggested at the outset it 


is seen that: | 
No. 


6 =the 14 grade. 
No.7 =the 14 < 
No. 8 =the 13 os 
No.9 =the No.2 


Now, since by careful rating the operator found that 
the strength of No. 5 is equal to that of No. 6, sample 
No. 5 must test 14. Since No. 4 was found to be half- 
way between 6 and 7, that is to say, half-way between 
14 and 14, sample No. 4 must test 13. No. 3 was 


CLASSIFICATION AND TESTING OF GLUES 49 


found to be half-way between 14 and 1?. Hence it 
tests 18. Nos. 1 and 9 being equal in strength, the 
former must test No. 2 grade; and as No. 2 was found 
equal to No. 8, it is of 1? test. 

Doubtless the reader is now able to appreciate more 
fully the importance of standards in glue testing. If 
these be incorrect the whole test is worthless, no matter 
how carefully conducted. 

We shall now extend our hypothesis by assuming 
that the samples, Nos. 1 to 5 inclusive, bear price marks. 
It is in order to check the price that we have deter- 
mined their strength. Comparing the test data side by 
side with the assumed price of each glue: 


Sample No. 1, testing No. 2 grade, is offered at 64 cents per lb. 
Sample No.2, “ 13 bbe Weg eae Je he 
Sample No.3, ‘“ 18 La COM Weegee atc 
Sample No.4, ‘“ 12 ETS SOE a5 By Pe Re aa 
Sample No. 5, 6c 14 “ “ c “44 & Ge 16s 





We cannot here enunciate any set rule governing the 
price of the various grades. Much depends upon cost 
of stock, labor, etc.; but if we assume that the above 
glues were offered for sale at a time when market 
conditions were normal, several valuable inferences may 
_ be drawn from the above hypothesis. In the first place, 
a 1} glue at 14 cents per pound is a luxury; all the more, 
a 12 glue (four grades weaker) at 12 cents. The prices 
assumed for the other grades in the table are about 
right. It is evident that the manufacturer is either 
endeavoring to impose upon the consumer in the cases 
of No. 5 and No. 3, or else he is compelled to ask the 
suggested prices for those glues, owing to the fact that 
his yield was lower than anticipated while the cost of 


50 GLUES AND GELATINE 


production was unusually large. We may simplify the 
entire hypothesis by assuming that the consumer applied 
to the manufacturer for samples of glues at 12 cents 
per pound, this being the price he was accustomed to 
pay for his glue, and that the manufacturer accordingly 
submitted the above five samples, all quoted at this 
price. Because of the test, the consumer is speedily 
enabled to decide upon a choice. 

Simple as is this finger test, it may be made, by dint - 
of practice and experience, remarkably accurate. The 
author has carefully compared the results obtained by 
it with those furnished by the use of the so-called 
testing machines, and the verdict is decidedly in favor 
of the finger test. To insure its success, the operator 
must, of course, be entirely free from bias. ‘The glasses 
should all be numbered and the numbers identified - 
only after the glues have been carefully rated. In this 
way the test is a fair one. Its accuracy, of course, 
presupposes that all the glues tested have been treated 
exactly alike. This is essential to the success of any 
system. i 

THE TEST SYSTEM AS A WHOLE 


A. Apparatus Required. 

1. Glasses. — The bar glasses commonly known as 
‘“‘sours”’ are best adapted to glue testing. These may 
be had of any dealer in hotel or bar supplies, and are 
much more durable than beakers. Only those having 
fairly thin bottoms should be selected, and to minimize 
danger of cracking while in the melting bath, the glasses 
should first be tempered. ‘This is done by filling them 
with cold water, placing them in cold water in the bath, 


CLASSIFICATION AND TESTING OF GLUES ol 


and slowly raisiig the temperature of the bath to boil- 
ing. The glasses are then removed and the contents 
permitted to cool to room temperature. They are 
then freshly filled with cold water and the operation 
repeated, save that this time the hot contents are 
immediately thrown out and the empty glasses held in 
a stream of cold water from the tap. Some will break, 
but those that survive the treatment will seldom crack 
through alteration of the temperature of the bath, and 
will be of service for a long time. 

2. Glue Melting Bath.— This consists of a trough, 
preferably of galvanized iron, provided with a false 
bottom resting about two inches above the true, and 
perforated with one-inch holes. Upon this the glasses 
rest, and in this way cracking from unevenness of flame 
is avoided. The sides of the bath should be of such 
height as to correspond with that of the glasses as they 
rest upon the false bottom. The bath should accom- 
modate thirty-six glasses. 

3. Scales. — A fairly accurate balance is required for 
weighing out the samples. The pharmacist’s prescrip- 
tion balance serves nicely, although less expensive forms 
of apparatus may be employed. 

4. Viscosimeter. — The different forms have already 
been described. 

5. Egg-beater.— This is required for the foam-test. It 
should be of the rotary form provided with a side wheel. 
For this test, there is also required a fairly stout glass 
jar, just wide enough to accommodate the egg-beater. 

6. Brush. — For the grease test, a flat brush, 1} 
inches wide and evenly trimmed, is required. In addi- 
tion, some aniline color should be on hand. 


02 GLUES AND GELATINE 


B. Procedure. - 

1. Selection of Standards. — Extended experience in 
glue testing will enable the operator to form some 
preliminary estimate of the strength of the glue to be 
tested. He cannot say with any degree of certainty 
what grade it tests, but he can roughly gage the limits 
within which it les. In this way, the experienced 
tester has only to use the minimum number of stand- 
ards. As arule, the eleven standards should be placed 
on test with the unknown samples, be the latter few or 
many. If the glues submitted be high-priced, it is to 
be inferred that they are high-grade, and accordingly, 
such standards as A Extra, No. 1, 14, should be selected 
for the comparison. Where any doubt exists, however, 
it is safest to employ all eleven standards. 

2. Weighing out the Glues. —'The samples and stand- 
ards having been numbered, the glasses are numbered 
to correspond and placed in single file in numerical 
order, beginning at the left. Twenty-five grams (or 
one ounce) of each of the samples and standards are 
then weighed off and transferred to the glasses. If the 
weighing is done carelessly, the entire test is invalidated. 
Exactly the same weight of each glue must be taken. 

3. Softening, or Soaking the Glues. — No hard and 
fast rule can be formulated as to the time required for 
this, much depending upon the form of the dry glue. 
If in the flake, strip, or piece, and very thick, from six 
to eight hours is required. If ground, one half an hour 
may suffice. The best way is to let the glues soak 
over night and melt them for test the following morning. 

As the glues are transferred from the scale-pan to 
the glasses, each glass is provided with a stirring-rod. 


* 
— eo a | eh 


CLASSIFICATION AND TESTING OF GLUES 53 


One hundred cubic centimeters (or four ounces) of water 
are measured out with the utmost care and poured over 
the glue, and the latter stirred with the rod so as to 
insure uniform immersion. Exactly the same amount 
of water must be poured on each glue — not a drop 
more or less. 3 

4. Melting the Glues. — When the glues are properly 
softened, the glasses are placed in the bath. This is 
then heated, beginning with a small flame. Simulta- 
neously, the flame is started under the viscosimeter 
bath. Lest any skins form on the solutions while 
melting, these must be frequently stirred. The forma- 
tion of a skin will seriously interfere with the test. 
Further, the solutions must be uniform, else the figures 
obtained for viscosity will be inaccurate. The temper- 
ature necessary to the determination of viscosity has 
already been noted. 

In seeking the various factors, the following order is 
most convenient : 


(a) As the glues are melting the odor of the solution is noted. 

(b) When all are in solution, Acidity or Alkalinity is determined. 

(c) Next, the grease test is applied to each. 

(d) By this time the glues are sufficiently hot for the: viscosity 
test. ° 

From now on, care must be taken to prevent skin formation. 

Where a plain pipette is used for determining viscosity, 
this must be thoroughly rinsed in boiling water between 
each test. 

(e) The viscosity determined, the foam may now be estimated. 

(7) The glues are now removed from the bath and permitted to 
jell, when they are rated. 


5. Jelling or Cooling the Glues. — This requires es- 
pecial consideration, lest faulty practice invalidate the 


o4 GLUES AND GELATINE 


test. In the winter time, it suffices to let the glues 
remain a while in a cool place until jelled. They must 
never be allowed to freeze. The greatest difficulty in 
jelling the glues is experienced in hot weather, when a 
small refrigerator may be used. In this, the tempera- 
ture is about 40° F., which is just right for jelling the 
glues without interfering with the rating. When the 
glues have been removed from the bath, they should 
be stirred slowly for a time, and in this way partially 
cooled. If this is done, the final jelly will have a 
flawless surface which will aid the operator in the 
rating. 

It were superfluous to state that,- throughout the 
entire test, the glues must be treated exactly alike. 
Unless this is done, it is useless to go to the trouble of 
testing them. 

C. Recording the Test. 

Some record of the test must be kept for future refer- 
ence. Such records are apt to be cumbersome. In 
the following system the record is concise and contains 
full data concerning all points of interest. It serves, 
among other things, to describe the appearance of the 


dry glue, long after the original sample has been thrown | 


out. To effect economy of space, the description of 
all test factors is reduced to a system of mnemonics, 
to wit: 

In describing or defining odor, grease, foam, alkali or 
acid, 

1 = None; 2 = Slight; 3 = Moderate; 4 = Considerable. 

In describing the appearance of the glue jelly, 


1 = Clear; 2 = Translucent; 3 = Dense. 


FS % fe 
nS a id - . : 
Oe ee 


CLASSIFICATION AND TESTING OF GLUES 55 


In describing the form of the dry glue, 


1 = Flake; 2 = Ground; 3 = Strip; 4 = Sheet; 5 = Powdered; 
6 = Shred; 7 = Ribbon. 


In describing the color of the glue, 


1 = Light Yellow; 2 = Medium Yellow; 3 = Dark Yellow; 
4 = Light Brown; 5 = Medium Brown; 6 = Dark Brown; 
7 = Opaque; 8 = Colored; 9 = Colorless. 


In describing the cut of the glue, 


1 = Very Thin; 2 = Thin; 3 = Medium; 4 = Thick; 5 = Very 
Thick. 


The following is a specimen test record used by the 
author. The various columns record the name of the 
sample, viscosity, odor, grease, foam, alkali, acid, ap- 
pearance of the jelly, and strength. In the last column, 
the litmus strip which has been used to determine the 
reaction is pasted by means of the tested glue adhering 
to it. In the upper left-hand corner of the space for 
recording the name of the sample are placed small 
numbers, describing, the color, cut, and form of the dry 
glue. Thus, No. 1, KA, is a dark yellow, ground glue; 
No. 2, H, is a medium yellow, thin flake. Samples 
Nos. 6 and 7, which are gelatines, are described as 
medium yellow, medium thick sheets. 

From the complete recorded description of sample 
No. 3, it is seen that this has a viscosity of little more 
than 24 seconds, has no odor, is free from grease, foams 
slightly, no alkali, slightly acid, jelly is fairly clear, and 
the sample tests 1 X. 


56 GLUES AND GELATINE 


25 Grams GLUE TO 100 c. c. 


Date, September 28, 1904. Test Sheet No. 47. 
S|ale| 3 
SampLE No. | Visc.| A | &| S| & | ActD|Jetty| SnorH. | Reaction 
O;/O/;/H/ a2 

32 

Nea FCO We 27 |} 1|2{|2)/1/ 14 | 14 |1Extra|Acid Strip 
221 

7h Mapes lenges 22. 50-4 tS SSeS a 1} ed 

3. de BONG, 1) 244i 1s lala 13 1X = 

4. JB. No.2): 22.4014 Die ee 14 14 3 

Be dat: ere] Bae: oh | hae eee 4; No.1 1 

234 

Go). Bei G iy 2S 11 | 24 2a) aes 14 |AA Ex “ 

234 

LAB We osu) 28p) La Used eda 14 | AA Ex " 

8. Crown... :/:194) 1 [D2 8b eee 13 e 

GON LW.) 1741 era et Tee 1 No. 2 3 
10. B. Sheet. .} 224 | 1} 2) 21-17 °2 1 No. 1 * 
113P. Be Nout) 164 oo iat oa eae 1 No. 2 4 
123P, BONO; VT Doel ate ee uf No. 2 . 
13. Pi BeNosap dst a Lora chee 1 No. 2 3 
14, P. B, 0...) 163 1-14-2493 | 1 [024 ee * 
15.1 Extra..|° 29 }.. | ee 1 Extra}, Sat Sees 
LGela Pore 24. Na lest le foe ee De oss wee 
LT ie aos 74 Oe rae Peres Meri ears 1g ee ee 
ih. 2G Sere eer 18? 0 2 ee 1g eee 





The value of keeping test records in this form can 
hardly be overestimated. A year may elapse from the 
time the operator has tested a certain glue when he is 
again called upon to test it. By referring to the original 
test, he may readily compare the two samples. In a 
separate index, the author notes the number of the test 
sheet upon which a given glue appears. For example, 
against the entry J.B.O. is the number 47, which is 
that of the above test sheet. | 

Some slight modification of the above test system is 


Pout St. « 


~~ —— ee 


CLASSIFICATION AND TESTING OF GLUES 57 


to be made in testing gelatines. Here the observer is 
concerned with the amount of water absorbed by the 
gelatine, its odor, reaction, grease, and foam. He may 
omit the determination of jelly strength. On the other 
hand, this jelly strength is directly proportionate to 
the amount of water absorbed, and if the sample of 
gelatine is tested in the same way as glue, the factors 
are easily determined. 

A study of the viscosity column of the above test 
record will confirm what has already been said relative 
to the inadequacy of viscosity as the ultimate measure 
of glue strength. Compare the viscosities of Nos. 6 
and 7, which are high-grade gelatines and which test 
two grades stronger than A Extra, with the viscosity of 
No. 15, the 1 Extra standard. Had we relied solely 
upon their viscosities to rate these two, we should have 
placed their strength at only 1 Extra. 

The author has tested more than thirty thousand 
samples of glue and gelatine, using no other test method 
than the one here described and relying invariably upon 
the finger test for the ultimate rating of the glue, in 
preference to using any test machines. The results 
have always been concordant. Proceeding carefully, 
two operators will differ only by two points within a 
grade, this difference being attributable to personal 
equation. So long as all the glues are treated alike 
and the operator is careful to eliminate personal bias, 
the test is an accurate one, the results agreeing closely 
with variations in price of the glues. ; 


CHAPTER III 


ANALYSIS OF GLUE AND GELATINE 


In discussing the methods applicable to the assay of 
the constituent elements of glue and gelatine, as well 
as of the impurities they may contain, it must be 
reaffirmed at the outset that analysis supplies no 
data as to the strength of the product. For the de- 
termination of this, the glue test is essential, sufficing 
for all practical purposes to acquaint the consumer 
with the relative merits of his purchase. As his expe- 
rience in testing increases, he will be able to account 
properly for all undue characteristics. 

Glue is in the main employed as a binding or adhesive 
medium; and its relative value for such use is compre- 
hensively determined by the test. In the more extended 
applications of glue and gelatine, however, where, for 
example, the latter is used for alimentary purposes, or 
the former for finishing delicate fabrics or for sizing 
sensitive colors, it may not suffice merely to know the 
relative economy of the product in actual work. Both 
glue and gelatine enter frequently into the manufacture 
of complex products in which they are compounded 
with chemicals. In such instances the question of purity 
has largely to be considered, the manufacturer having 
often to purchase the glue and gelatine upon specifica- 
tion. Excesses of grease or soaps, acid or alkali, mucin 

58 


ANALYSIS OF GLUE AND GELATINE 59 


or foreign mineral matter may all operate to the disad- 
vantage of his processes. It is for chemical analysis 
to determine these limits; and the results of analysis 
often serve to amplify and confirm the qualitative 
observations of the test. Hence, where time permits, 
analytical data should be collected for such comparison. 

The analysis of glue and gelatine comprehends the 
determination of moisture, ash, acidity, or alkalinity, 
fat, foreign matter and available glue present. It 
includes also the qualitative recognition of mucins. 

1. Moisture. — A good glue contains not less than 

8 nor more than 16 per cent of moisture. Moisture in 
excess renders the finished product more or less pliable 
and soon causes putrefaction. If too dry, on the other 
hand, the glue soon becomes brittle and gradually 
crumbles away. In this condition, it has lost much of 
its original strength. 
' To determine the content of moisture, about three 
orams of the sample, preferably in the ground. or 
powdered state, are weighed out upon a tared watch- 
glass and dried in the oven at 110° C. to constant 
weight. The loss in weight represents the moisture 
which may be calculated to per cent based upon the 
weight of the sample taken. 

2. Ash. — The dried sample from the moisture de- 
termination is transferred to a weighed platinum cruci- 
ble. This should be capacious, so that the sample may 
be distributed over the bottom in a fairly thin layer. 
Neglect of this precaution will retard incineration. 

A small Bunsen flame is now placed underneath 
the crucible and gradually raised until the bulk of the 
carbon has been burned off. During incineration the 


60 GLUES AND GELATINE 


glue swells, the contents of the crucible suddenly 
bursting into flame. At such times, the Bunsen flame 
should be withdrawn and the contents be permitted to 
burn quietly of their own accord. Incineration may be 
completed over the blast-lamp, although, if proper 
precautions have been observed, a pure white ash may 
be obtained with the heat of an ordinary Bunsen flame. 
Too much heat at the outset produces a form of carbon 
which is extremely difficult to burn off completely. 
After the glue has been reduced to an ash, it should 
be observed if this has fused or not. This will serve to 
identify the glue as bone or hide, as the case may be. 
The ash of bone glue fuses and its aqueous solution is 
neutral, containing traces of phosphates and chlorine. 
The ash of hide glue does not fuse, owing to the presence 
of traces of lime which render its aqueous solution 
slightly alkaline. The solution is free from phosphates 
and chlorides. 3 
In the ash will be found traces of media added to the 
glue to produce “color,” which may be identified by 
applying the usual qualitative tests. At times such 
salts will be found, as the carbonate and the sulphate 
of lead, chromates and the salts of tungsten which have 
been added with a view to increasing the adhesiveness 
of the glue or to facilitate the drying of the solution. 
The presence of such salts as sulphate of barium, car- 
bonate of calcium (chalk); carbonate of magnesia, or 
zinc oxide or sulphate, must not be construed as 
adulteration; other salts may properly be so regarded. 
The ash will vary from 2 to 8 per cent, according to 
the quality of the glue. Its examination is of interest 
as confirmatory of certain test factors. Thus, it has 


ANALYSIS OF GLUE AND GELATINE 61 


already been pointed out that the viscosities of acid- 
treated bone glues, or of glues from mixed bone and 
hide stocks, are disproportionate to their jelly strengths, 
the latter being higher than the viscosity would indicate. 
Accordingly, if a given glue display this disrelation 
between viscosity and jelly strength, and yet the jelly 
be not sufficiently clear to warrant the assumption that 
the glue is from acid-treated stock, the examination of 
the ash will doubtless prove it to be a mixture of bone 
and hide, the ash partially fusing and its solution 
showing lime, phosphates, and chlorides. 

A very clear glue may have a viscosity much higher 
than normal and its ash may contain alum. This is 
proof of the fact that the glue-liquor was clarified by 
means of alum, or that the alum was added with the 
deliberate intent of imparting to the solution of the 
finished glue a fictitious “body.”’ Alum precipitates 
much of the viscous element (chondrin) of glue, but, if 
used in excess, the precipitate redissolves and thus the 
glue solution becomes very “stringy.” The use of an 
excess of alum in clarification invariably produces a 
foamy glue. These two phenomena are to be observed 
in rabbit glues, some of which test A Extra, having 
viscosities of 70 seconds. The ash of these glues is 
rich in alum | 

3. Acidity and Alkalinity. — For the determination 
of alkali, one gram of the sample is dissolved in 500 ec. ce. 
of distilled water, so as to form a practically colorless 
solution. A few drops of alcoholic solution of phenol- 
phthalein are added and the whole titrated with deci- 
normal hydrochloric acid until the pink coloration just 
disappears. 


62 GLUES AND GELATINE 


In the case of acidity, direct titration of the glue 
solution with standard alkali would supply figures 
representing the sum of mineral and free organic acids. 
Hence, for the determination of mineral acidity, 50 
grams of the sample are suspended in a flask in 
80 c. c. of cold distilled water for ten hours. The flask 
is then fitted to a condenser and the volatile acids 
driven over by means of a current of steam, the distillate 
being collected in a graduted cylinder. When 300 ec. c. 
have come over, the distillation is interrupted and the 
distillate is titrated with standard alkali. In the pres- 
ence of sulphurous acid, the cylinder should contain a 
known quantity of standard alkali added previous to 
distillation. The figures obtained represent acidity due 
to hydrochloric and sulphurous acids, which should not 
exceed 0.2 per cent. 

For the determination of free organic acids in addi- 
tion to sulphurous acid, Kalmann proposes the following 
method: 

One gram of the coarsely powdered glue is dissolved 
in water over the water-bath and then titrated with 
standard alkali, using phenol-phthalein as an indicator. 
The liquid is now cooled and, after the addition of some 
starch solution, is titrated with decinormal iodine until 
a permanent blue color is established. The amount of 
iodine used is the equivalent of the sulphurous acid in 
the sample. | 

The blue color is now discharged by the addition of 
a drop of sodium acid-sulphite and again titrated with 
decinormal alkali and phenol-phthalein.. The second 
volume of alkali indicates the amount of hydriodic acid 
formed, which should correspond with the result of the 


ANALYSIS OF GLUE AND GELATINE 63 


lodine titration, showing that this was in no wise 
affected by the organic matter of the glue. 

4. Grease. 

(a) Kissling’s Method. — Twenty grams of the sample 
are dissolved in 150 c. c. of water containing 10 ¢. c. 
of hydrochloric acid, 1.20 specific gravity. The liquid 
is heated three or four hours under a reflux con- 
denser on the water-bath. The solution is cooled, 
50 c. c. of petroleum ether added, and the whole well 
shaken, when, after standing until clear, an aliquot part 
of the solvent is withdrawn into a weighed dish, the 
solvent evaporated, and the residual grease weighed. 

(b) Hztraction Method. — This is by far more con- 
venient of operation than the foregoing. 

About five grams of the finely ground or seen 
sample are covered with an equal weight of water, 
soaked up and melted over the water-bath. An absorb- 
ent material is now added to remove the water. S. 
Rideal recommends plaster of paris. The author finds 
that this seriously interferes with the drying of the 
mass and uses fine infusorial earth which has previously 
been well extracted with petroleum ether, and kept in 
a tightly stoppered bottle. The mass; when dry, is 
placed in a mortar and carefully reduced to powder. 
This must be done cautiously, as some is apt to spatter 
while grinding. It is best first to break the mass 
roughly on a large sheet of paper and transfer small 
portions at a time to the mortar, and so powder 
them. 

- The powder is now transferred to the capsule of the 
Soxhlet extraction apparatus, and extracted with pe- 
trolic ether for two hours. At the end of this time the 


64 GLUES AND GELATINE 


flask containing extracted grease and solvent is con- 
nected with a condenser and the bulk of the solvent 
distilled off. The balance is transferred to a weighed 
dish, the flask rinsed well with the smallest possible 
quantity of fresh solvent, the washings added to the 
contents of the dish, and the whole cautiously evapo- 
rated over the water-bath. The residual grease or fat 
is then weighed. 

5. Approximate Assay of Constituent Elements. 

(a) Gelatin. — Gelatin is distinguished from chondrin 
and mucin by certain characteristic reactions. Its assay 
in glue is of but little interest, but in ascertaining the 
purity of commercial gelatine, it is a factor of impor- 
tance, a good gelatine consisting chiefly of gelatin and 
little else. 

(aa) Preparation. — For the purpose of confirming 
its qualitative reactions, pure gelatin may be obtained 
as follows: 

1. Method of Davidowsky. — Buckshorn is treated 
with dilute hydrochloric acid for the purpose of dis- 
solving out the calcium phosphate, leaving the glue- 
yielding material. The latter is treated with milk of 
lime to free it from fat, washed, boiled and the result- 
ant solution permitted to jell. The jelly is now treated 
with successive cold waters which serve to extract all 
coloring matter. This accomplished, the jelly is dis- 
solved, strained and mixed with an equal volume of 
95 per cent alcohol, a precipitate of gelatin resulting 
which may contain phosphates. These may be re- 
moved by redissolving the precipitate, acidulating the 
solution, and bringing it into a dialyser, where the salts 
and acid diffuse in the water which must be renewed. 


ANALYSIS OF GLUE AND GELATINE 65 


A jelly of pure gelatin remains behind. This is evapo- 
rated to driness. 

2. Method of Allen. — High-grade gelatine is soaked 
in successive quantities of cold water for several days. 
This removes salts and coloring matter. It is then 
dissolved in boiling water and filtered into 90 per cent 
alcohol, which precipitates the gelatin in white, stringy 
masses. These are collected, redissolved in hot water 
and reprecipitated by alcohol. The ash of the product 
is about 0.6 per cent. 

Pure gelatin, in the dry state, 1s fairly transparent 
and glassy in appearance. It is somewhat yellowish and 
free from odor. It is not affected by exposure to the 
air. When heated, it softens without melting, swells 
considerably and decomposes with an odor resembling 
that of burned hair. The ash is blackish and com- 
bustible only with great difficulty. 

Gelatin is insoluble in cold water, in which it swells 

and loses its transparency; but in hot water it dissolves 
with subsequent formation of a strong jelly. This may 
be re-melted and re-jelled a number of times, but pro- 
longed treatment destroys the gelatinizing property, 
although this is said to be restored by precipitating the 
gelatin by alcohol from the final solution. (Alien.) 
- Gelatin is precipitated from aqueous solution by 
chlorine, alcohol, platinic chloride, tannin, mercuric 
chloride, picric, phospho-molybdic, and phospho-tungs- 
tic acids and acid solution of chromic acid. 

When a current of chlorine is passed through a solu- 
tion of gelatine about one per cent in strength, the liquid 
remains clear for a time, but after a while froths strongly, 
each particle of froth becoming encased in a white 


66 GLUES AND GELATINE 


pellicle. The frothing subsides as soon as the chlorine 
is In excess, which is noted from the yellow color of the 
solution, the liquid becoming clear and the gelatin is 
thrown down in the form of a white, granular precipitate. 
This, when washed and thoroughly dried, is a fairly 
white powder insoluble in water or alcohol, but soluble 
in alkalies. 

Addition of a saturated aqueous solution of picric 
acid to a cold aqueous solution of gelatine produces a 
precipitate which first dissolves upon shaking, but which 
becomes permanent upon the addition of an excess of 
the precipitant. Upon heating, this precipitate is dis- 
solved, but is again formed as a yellowish, sticky mass, 
as the solution cools. Platinic chloride and sulphate 
produce much the same precipitate. 

Gallotannic acid precipitates gelatin as a fine white 
powder, which, upon exposure to the air, becomes buff- 
colored. Once thoroughly dried, this is soluble only in 
strong alkalies. ; 

(b) Chondrin. —The distinction between chondrin 
and gelatin was first pointed out by Muhlder. These 
have several reactions in common, but chondrin is 
precipitated by a number of substances which fail to 
react with gelatin. ~ 

(bb) Preparation. — For the preparation of pure 
chondrin, Davidowsky recommends the selection of the 
cartilages of the ribs, of the larynx — with the exception 
of those of the epiglottis, and of the windpipe and 
bronchi. These are boiled from 24 to 48 hours, the 
chondrin precipitated from solution by alcohol, re-dis- 
solved in warm water, evaporated, and dried.. The 
product so obtained closely resembles gelatin. 


ANALYSIS OF GLUE AND GELATINE 67 


Like gelatin, chondrin is precipitated from aqueous 
solution by alcohol, tannin, and mercuric chloride. 
Unlike gelatin, it is precipitated by mineral acids 
orgamc acids, alum, sulphate of alumina, acetate and 
subacetate of lead, and sulphate of iron. All of these 
precipitates are soluble in excess of precipitant. 

Of the precipitates produced by acids, those from 
phosphoric, hydrochloric, nitric, and sulphuric are sol- 
uble in excess; whereas, those from pyrophosphoric, 
sulphurous, hydrofluoric, carbonic, arsenic, tartaric, citric, 
oxalic, lactic, and succinic are insoluble in excess of 
precipitant. 

(ce) Mucin. — While this is in no sense a constituent 
element of glue, it 1s properly discussed in connection 
with gelatin and chondrin, since, like them, it emanates 
from the glue-yielding tissues. Its presence in glue is 
due to defective liming or faulty washing after liming. 

Mucins are slimy substances which mix with water 
in all proportions without undergoing real solution. 
They may be precipitated by alcohol or by saturation 
with common salt, ammonium sulphate and other 
neutral salts. They are soluble in alkalies and a 10 
per cent solution of common salt. 

Estimation of Glue Content.— This is at best only 
approximate, indirect methods of calculation supplying 
more reliable results than direct. The latter are based 
upon the precipitation of the gelatin and chondrin by 
tannic acid, and: either weighing the precipitate of 
“tannate of gelatin,’ which is assumed to have the 
composition — tannin 57.26 per cent, gelatin 42.74 per 
cent; or estimating the nitrogen content of the precipi- 
tate and calculating this to gelatin. An optional method 


68. GLUES AND GELATINE 


is to determine the total nitrogen content of the glue, 
calculating the result to gelatin. 

Rideal has pointed out the complexity of the organic 
matters of glue. Besides albumoses and _ peptones, 
several varieties of gelatin and chondrin may be present, 
as is evidenced by differences of elementary composi- 
tion revealed by analysis. Each variety exerts a vari- 
able precipitating influence upon the tannin, which, in 
addition, throws down the peptones and other non- 
gelatinous matter. Through co-estimation of these with 
the gelatin and chondrin, the figures obtained are 
extremely inaccurate. Equally unsatisfactory is the 
estimation of the nitrogen content of the glue, this 
being that of all the nitrogenous matters present whether 
gelatinous or not. , 

For technical purposes, it suffices to estimate the 
non-glue, comprising fats, soaps, and extraneous 
mineral matter, and calculating the available glue 
by difference. This method fails to take into account 
such non-gelatinous’ substances as albumoses and. 
peptones. 

Stelling’s Method. — Fifteen grams of ‘the sample — 
are placed in a 250 c. ¢. flask, covered with 60 ec. ec. 
water and soaked over night. The following morning, 
the mass is melted and any loss through evaporation 
made good. The flask is then made up to the mark 
with 96 per cent alcohol and the contents thoroughly 
shaken. After standing for about six hours, from 25 to 
50 c. c. of the supernatant liquid are withdrawn, evapo- 
rated to driness, and the residual non-glue dried and 
weighed. 

In criticism of the above method, Kissling points out 


ANALYSIS OF GLUE AND GELATINE 69 


that the non-glue consists of fat as well as decomposition 
products of gelatin. He also observes that gelatin is 
not totally insoluble in alcohol of 72 per cent strength. 
Nevertheless, he considers the method reliable as par- 
tially indicating the value of a glue. He found that 
the non-gelatin varied from 7.6 per cent in the case of 
a hide glue, to 23.2 per cent in a very inferior bone 
product. 

By Stelling’s method, any mucin present is thrown 
down by the alcohol and hence is not estimated with 
the non-glue, thus rendering the figure for available glue, 
obtained by difference, high. This is not a very serious 
objection inasmuch as, when present in glue, the amount 
of mucin is quite small, the presence of even this ren- 
dering the glue unfit for many uses. Hence its co- 
estimation indirectly with the true glue occasions no 
serious error. On the other hand, the substances pre- 
cipitable by alcohol carry down with them much, if not 
all, of the media added to the glue to produce color. 
Hence, in the case of opaque or colored glues, the color- 
ing material must be estimated separately and added 
to the figure for non-glue. The author does not regard 
as pertinent Kissling’s objection to the .co-estimation 
of fat with the non-glue. True, if much grease be pres- 
ent in the residue of non-gelatinous material it will 
interfere with accurate weighing because of its hygro- 
scopic nature. For this reason, it is well to extract the 
grease before estimating the non-glue. In all instances, 
however, the figure for grease must be added to that 
for non-glue. Again, the glue should be dissolved in 
not more than twice its weight of water that the subse- 
quent dilution of the alcohol may not be so great as te 


70 GLUES AND GELATINE 


permit the return of any of the precipitate to solution. 
With these modifications, the method yields reliable 
results; and it will be found that the figures for true 
glue, calculated by difference, are well in accord with 
the grading assigned by test. 

Foreign Matter. — This includes insoluble organic as 
well as mineral matter. For the determination, about 
two grams of the glue are soaked and dissolved in a 
liter flask with the aid of 200 c. c. of water. The flask 
is then made up to the mark, care being taken to mix 
the contents thoroughly. The flask is then kept in a 
warm place from 24 to 48 hours, during which the 
insoluble material settles to the bottom. The bulk of 
the supernatant solution is decanted off, the balance 
being poured through a tared filter and the residue 
washed with hot water until free from all glue. The 
filter, with its contents, is then dried at a temperature 
not exceeding 100° C. and weighed. The figures so 
obtained serve to correct the result for available 
elue. 

Both glue and gelatine exhibit characteristic behavior 
toward certain reagents, the reactions serving to iden- 
tify them when associated with other substances, and 
frequently to separate them quantitatively. 

Gallotannic acid produces a buff-colored precipitate, 
known as tanno-gelatin. This is supposed to be the 
chemical base of leather. The reaction takes place in 
solutions containing only 0.005 per cent of glue or 
gelatine. 

Added to a neutral or slightly alkaline solution of 
gelatine, formaldehyde produces a white, stringy pre- 
cipitate of formo-gelatin.. The purer the product, the 


ANALYSIS OF GLUE AND GELATINE (fl 


more readily the precipitate forms, low-grade glues 
requiring some time to respond to the test. 

The bichromates of potassium and ammonium, added 
to solutions of glue and gelatine, render the product 
evaporated therefrom insoluble after exposure to sun- 
light. , 

When compounded at high temperature with dilute 
mineral acids, glue loses its power of gelatination. This 
is restored by the addition of common salt. 

A glue solution boiled with slaked lime loses its 
gelatinizing power; and if the solution be subsequently 
evaporated, the product is a colorless, gummy mass, 
soluble in cold water and a solution of common salt. 

Potassium or ‘Sodium carbonate, neutral potassium 
tartrate, magnesium sulphate, and rochelle salts coagu- 
late glue solutions by removing the water from them. 

Gelatination may be destroyed by the addition of 
the chlorides of ammonium and barium, nitrate of 
potassium, and saturation with common salt. 

Glue and gelatine are distinguished from albumins in 
that they yield no precipitate with potassium ferrocya- 
nide or ferricyanide. 

Purity of Commercial Gelatine. — For this, Vogel em- 
ploys a 10 per cent solution of silver nitrate to which 
has been added enough ammonia to re-dissolve the 
precipitate which first forms. This reagent is then 
mixed with an equal volume of the solution under 
examination. Any impurity is indicated by a coloration 
varying from yellow to deep brown. 


CHAPTER IV 


GLUE AND GELATINE SUBSTITUTES 


WuereE adhesiveness is the chief end to be attained, 
proteid substances other than glue, as well as a number 
of vegetable products, may be used in the place of glue. 
Certain alge gelatinize from solution and hence are 
available as substitutes for gelatine inssome classes of 
work. At times these products aroffabetitutea ith: 
out the purchaser’s knowledge; at others, he knowingly 
selects them in the belief that they are cheaper than 
glue. It is to be borne in mind {Rat they are avail- 
able as glue substitutes only for the purpose of adhe- 
sion, and even then they are not as economical, in 
actual work, as glue, although they possess some of 
the characteristics of the latter. In certain industries, 
notably in the manufacture of paper boxes, it is desir- 
able to employ an adhesive which, while it binds, 
does not jell. Hence the use of such agglutinants as 
“Tiquid Glue” and ‘Boston Gum,” both of which 
may be used cold on the topping-machine. The use of 
glue substitutes in such case is not open to adverse 
comment. On the other hand, the abuse of the pur- 
chaser’s credulity to the extent of offering dextrine 
or gum crystals as glue is to be condemned. 

In the early days of the glue industry, it was a com- 


mon practice to adulterate ground glues with rosin. 


72 





GLUE AND GELATINE SUBSTITUTES 73 


Sand was also used to a limited extent; and it is the 
recollection of these practices, long since abandoned, 
that actuates 90 per cent of latter-day prejudice 
against ground and powdered glue. A more modern 
attempt at adulteration is the endeavor to combine 
corn dextrine with ground glue. The dextrine 1s first 
dissolved, the solution evaporated to driness, and the 
resultant product ground and mixed with the glue. In 
times of glue scarcity, when the price of all grades is 
abnormally high, the consumer naturally turns to some 
cheaper product that will answer his requirement; and 
it is in this way that the majority of glue substitutes 


have come into,use. 

Casein. —_wikn the sugar of milk ferments, pro- 
ducing lactic acid, the milk turns sour, and casein, the 
characteristic proteid of milk, is separated in a coagu- 
lated mass. The entire phenomenon is due to the 
action of the Bacterium Lactis. Casein is also produced 
when acetic acid is added to fresh milk, if this be diluted 
and warmed. Exact neutralization with acid does not 
precipitate the casein owing to the interference of the 
alkaline phosphates present in the milk. An appre- 
- ciable excess of acid must be employed. | 

A somewhat modified: form of casein is obtained by 
the treatment of milk with rennet, a ferment extracted | 
from the fourth stomach of the sucking calf. This 
contains the enzyme rennin or chymose, which coagu- 
_ lates the milk, the casein separating and the milk-sugar, 
lactalbumins, ete., remaining in solution. The casein 
so obtained differs from that produced by the addition 
of acid to the milk, in that the latter form is a precipi- — 
~ tate which, under suitable conditions, can again be 


74 GLUES AND GELATINE 


obtained in solution; whereas the action of the rennet 
is true coagulation and the casein is insoluble in any 
media save such as change its chemical constitution. 
Commercial casein is purified by alternate solution in 
alkali and precipitation with acid, the precipitate being 
thoroughly washed each time. The number of these 
. treatments determines its purity and hence its price. 
According to purity, the color of the dry product varies 
from brownish-yellow to almost white. Casein is insol- 
uble in cold water (1 part to 1000), and in hot water 
swells to a sticky paste without undergoing real solu- 
tion. It is readily soluble in weak alkalies and weak 
acids. To facilitate solution, casein is frequently mixed 
with 12 per cent of borax, the mixture coming into the 
market under the name Soluble Casein. Caustic alka- 
lies exercise a drastic action on casein, deepening the 
color of the solution and imparting a disagreeable odor. 
The application of casein to the arts is varied. It is 
useful as a substitute for albumin in ealico printing. 
Upon evaporation from ammoniacal solution, casein is 
only partially soluble in alkalies, and if the solution of 
casein in ammonia be treated with milk of lime, the 
casein, upon evaporation of the solution, is fast to all 
washing and soaping. Dolfus converts the casein into 
a nitro-compound, and this is dissolved with the aid of 
caustic soda, the consistency of the solution being 
reduced with water. When steamed, this becomes fixed 
in the cloth, resisting the action of soaping and chlorine. 
Casein is applied as the thickener for gold and alu- 
minum bronzes for printing silk. It is far cheaper than 
gum tragacanth, and yields even better results. : 
An insoluble compound results from the treatment of 


GLUE AND GELATINE SUBSTITUTES 75 


casein with slaked lime. This combination is useful as 
a cement for earthenware, etc. A water-proofing com- 
pound is obtained by: treating solutions of casein with 
formaldehyde. A small amount of formaldehyde suffices 
to produce the desired result, any excess precipitating 
the casein from solution. 

Casein is of service in the preparation of colored 
micas for printing wall-paper. The aniline color is 
precipitated upon the mica by some suitable reagent 
and the addition to the solution (hot) of a small quan- 
tity of casein serves to bind the color firmly to the 
mica. In the same industry, casein may be wholly 
substituted for glue as the medium for sizing the pulp- 
colors. Its use for this purpose is attended by difficulty, 
inasmuch as certain of the colors, when in combination 
with the casein, cause the latter to ferment, the mixed 
color and size frequently overflowing the barrel. 

Very serviceable insoluble lakes or pulp-colors may 
be prepared by precipitating casein from ammoniacal 
solution in conjunction with the color, by means of 
chloride of aluminium, stannous chloride or acetate. 

Egg- and Blood-Albumin. — The albumin of eggs is 
distinguished from that of blood-serum, etc., by the 
designation ALBUMEN. White of egg is a nearly pure 
solution of proteids, the chief of which is egg-albumin 
or ALBUMEN. Upon evaporation at 60° C., white of 
egg yields about 14 per cent of albuminous residue. If 
- the white of egg is thoroughly beaten with water, the 
albumin and salts pass into solution, membraneous 
material remaining behind. The albumin may be sepa- 
rated from the soluble salts by precipitation with basic 
acetate of lead, the precipitate decomposed with car- 


76 GLUES AND GELATINE 


bonie acid, and the lead removed with sulphuretted 
hydrogen. Coagulation occurs upon cautiously warm- 
ing the liquid to 60° C., the first flakes of albumin carry- 
ing down with them the last traces of lead sulphide, 
leaving the supernatant liquid colorless. This is evapo- 
rated at 35° C., when the albumen is obtained in pale 
yellow scales. (Allen.) 

Albumen may be obtained in the solid state by 
cautiously evaporating white of egg at a temperature 
below 50° C. It is fairly transparent and of a pale 
yellow color. It is frequently adulterated owing to the 
fact that it is more valuable than blood-albumin. - 

Blood- or serum-albumin results from the evaporation 
of the separated serum of perfectly fresh blood. The 
evaporation is conducted at about 50° C., when the 
albumin is obtained in the form of scales or flakes 
varying in color from grayish to black. Three or four 
qualities of blood-albumin are known, the purest being 
a dirty yellow, and the poorest, black. 

Both egg- and blood-albumin are applied to the 
printing of cotton fabrics, when they are rendered | 
insoluble by coagulation with steam, acting as mordants 
for a number of colors. Egg-albumin is also employed 
in silk printing as one of the ingredients of the color- 
thickener. It finds further application in the manu- 
facture of confectionery. Black blood-albumin is not 
used for printing fabrics, but is useful in sugar-refining 
and in dyeing with Turkey-red. Blood-albumin may 
be employed for printing all but the most delicate 
colors. It is cheaper than egg-albumin and has greater 
thickening power. Egg-albumin is largely substituted 
for gelatine in photography in the preparation of sen- 


: 


GLUE AND GELATINE SUBSTITUTES fp 


sitive coatings for printing-papers, which consist of 
albumen treated with silver haloids. The author has 
frequently been called upon for an opinion respecting 
“glue,”’ which has turned out to be nothing more than 
blood-albumin and sometimes egg-. It is difficult to 
understand how one could be inveigled into the purchase 
of albumin for glue, the characteristic odor of the former 
being sufficient to distinguish the two, as well as being 
so disagreeable as to bar it es many uses to which 
glue is adapted. 

Dextrine Crystals. — Dextrines result from the treat- 
ment of the corresponding starches with acids at various 
temperatures, the duration of the treatment determining 
the color as well as the solubility of the product. The 
best are those produced from potato starch, and in order 
of serviceability rank fapioca-dextrines, corn-dextrines 
and sago-dextrines. British gum is made from the 
various starches by simply roasting these for a certain 
length of time without the aid of acid. Its solution is 
heavier in body than those of dextrines, and is much 
lighter in color. | 7 

Canary potato-dextrine is of medium yellow color in 
solution, which, if prepared sufficiently concentrate, 
yields dark yellow crystals closely resembling the par- 
ticles of a ground foreign glue of light shade. These 
require preliminary softening or soaking prior to solu- 
tion, and this is similar in appearance and characteristics 
to the.solutions of weak animal glue, with the exception, 
of course, that the dextrine solution does not jell. 
Solutions of dextrine admirably fulfil the minor re- 
quirement of the paper-box maker, as they are as 
adhesive as weak glue. They have not equal binding 


78 GLUES AND GELATINE 


strength, however, nor are they cheaper than glue, as 
many would believe. They are readily prone to de- 
composition and molding, unless properly preserved 
with formaldehyde or carbolic acid. 

Gum Arabic. — This gum is too well known to require 
detailed description in these pages. It is extensively 
employed in the manufacture of mucilages, in conjunc- 
tion with dextrines. The poorer varieties are some- 
times substituted for glue. The particles of gum require 
long soaking before applying heat to bring them into 
solution, and the solution must be prepared very thick 
to equal in adhesiveness that of a weak glue. Under 
these circumstances, the gum is more costly than animal 
glue. The addition of some glycerine is necessary to 
impart sufficient flexibility to the dried gum. 

Japanese Gelatine, etc. — Certain algz or sea-weeds 
yield a highly gelatinous substance upon treatment with 
boiling water. Chief among these is the Gelidewm 
Corneum, familiarly known as Chinese Moss or Japa- 
nese Gelatine. Its chief constituent is gelose, which 
has ten times the gelatinizing power of isinglass, setting 
to a jelly when dissolved in five hundred times its 
weight of water. It occurs in commerce in bundles of 
long strips and resembles some forms of isinglass. It 
swells in cold water and is thoroughly soluble in hot. 
Upon cooling, the solution sets to a jelly which, al- 
though its melting point is higher than that of isinglass, 
lacks tenacity. The jelly is colorless and translucent, 
like that of a high-grade gelatine. 

Chondrus crispus, Irish Moss, is an alga gathered 
from the rocks at low tide on the west coast of Ireland, 
where it constitutes an article of diet. The greater 


GLUE AND GELATINE SUBSTITUTES 79 


part of the moss consists of the gelatinous substance, 
carrageenin, somewhat analogous to gelose, though 
yielding a far darker jelly. The jelly finds application 
in medicine and is also used in the manufacture of 
textile fabrics, either as a finishing size or as a thick- 
ening medium for printing colors on cotton or silk. 

Agar-Agar, the edible sea-weed of Ceylon and other 
localities, contains a gelatinous principle very similar 
to gelose. 

Gluten. — Starch-tailings, consisting mainly of gluten, 
or the latter itself, are the basis of the so-called dry 
pastes which are offered in place of regular flour-paste; 
and this substance is worthy of some consideration as a 
possible glue substitute. Wheat flour consists of starch 
and gluten, the latter containing the two proteids, 
glutenin and gliadin. When flour is kneaded in a bag 
under a stream of water, the starch gradually passes 
into solution and the gluten remains behind as a brown- 
ish, sticky mass. This dries to a grayish, brittle sub- 
stance which, though insoluble in cold water, is fairly 
soluble in boiling, the undissolved portions combining 
_ with those in solution to produce an extremely heavy, 
sticky paste. Solution of the dried gluten is facilitated 
by the addition of a small amount of alkali, and the 
gray color of the dried product is improved and whitened 
by the addition of chalk, silver white, and possibly a 
trace of ultramarine blue. 

Though somewhat more troublesome of manipulation 
than ready-prepared flour-paste, ‘‘dry”’ pastes are far 
more adhesive, owing to the greater content of gluten. 
The serviceability of regular flour-pastes is largely 
dependent upon the proper development of the gluten 


80 GLUES AND GELATINE 


of the flour. By treatment with a small amount of 
borax, cooking at a proper temperature, a flour-paste 
may be produced which is fully the equal, if not the 
superior, of weak glues in binding as well as adhesion. 
The author has seen such pastes bind two sticks of 
wood so that considerable force was necessary to break 
them apart; in one instance, the wood breaking before 
the cemented joint gave way. Jlour-pastes, well made, 
regular or “dry,” have largely supplanted glue in 
trunk-making as well as the production of leather 
novelties, such as bags, belts, and pocket-books. The 
heavy canvas covering of trunks is often laid on with 
good paste, which holds just as well as a medium quality 
of glue, and is far cheaper and easier of manipulation, 
requiring no preliminary soaking. 

Gluten has, of course, its disadvantages in use. It is 
prone .to rapid decomposition and putrefaction, the 
gases evolved being of the most unpleasant character. 
The problem of a proper preservative for flour-paste 
remains unsolved. Mercuric chloride is commonly em- 
ployed, in solution in hydrochloric acid. Hydrofluorie 
acid works well as does also formaldehyde, though 
the pungent odor of the latter is a decided disadvant- 
age. : 

“Liquid Glue.” — This is used in the manufacture of 
paper boxes, in conjunction with flour-paste, for the 
lighter work. It contains no animal glue whatsoever, 
_being a solution of British gum and light and dark canary 
corn-dextrine. To this, flour-paste is at times added 
with a view to increasing the ‘‘body” of the solution. 
“Liquid Glue”’ is dark brown in color and dries not unlike 
a solution of a weak, dark bone glue. Properly prepared, 


GLUE AND GELATINE SUBSTITUTES 81 


it is fairly adhesive in solution and is preserved with 
cresylic acid (crude “‘carbolic” acid), formaldehyde, etc., ’ 
an essential oil being frequently added to disguise the 
odors of the preservatives. 

Boston Gum. — A solution of dextrines, blackish in 
color owing to the admixture of crude phenol or cresylic 
acid as a preservative, is employed by some paper-box 
manufacturers in preference to “liquid glue.” It is 
extremely useful for “topping,’”’ as it may be run cold 
on the machine for this work. It excels “liquid glue” 
in adhesiveness. and resembles more closely than 
the latter a solution of weak animal glue. It has also 
the advantage in that it does not impair the gloss of the 
paper, as do many preparations of superior adhesiveness 
and binding power, which are made by bringing starches 
into solution in the cold with the aid of caustic alkali. 
These latter invariably dry to a dull coating. 

Preparations such as Brightwood gum, envelope gum 
and similar dextrine pastes or solutions are now used 
exclusively in the manufacture of envelopes where 
formerly glue was employed. 

Methods of Detection and Analysis. — Not only are 
some of the above-described products substituted for 
glue, but several of them are liable to adulteration. 
This applies particularly to commercial albumin, espe- 
cially egg, which is hocused to a great extent by the 
unscrupulous. 

In general, casein may be distinguished from albu- 
mins and all from genuine glue, by their characteristic 
odors. The odor of casein, whether dry or in solution, 
is markedly cheesy — a characteristic never observed in 
glue. The odor of albumin, while impossible of descrip- 


82 GLUES AND GELATINE 


tion, is easy of recognition, and once known is not easily 
forgotten. Solutions of dextrine are sweet to the taste 
and smell, unless these characteristics have been de- 
stroyed by preservatives. Gluten has an odor, when 
dry, not unlike that of stale crackers. In the wet state 
it preserves this same odor and is further recognizable 
from its consistency and appearance, which resembles 
that of an exceedingly dirty flour dough. 

Casein. — Though casein itself is not liable to adul- 
teration, it may be employed to adulterate glue or 
albumen. Solutions of casein are not coagulated by 
boiling, while those of albumins are. The casein may 
be precipitated from solution by an excess of common 
salt, magnesium sulphate, chloride of barium, and 
calcium. It is completely precipitated by the usual 
reagents for proteids — sulphate of copper, bichloride 
of mercury, acetate of lead, ete. 

When present in conjunction with glue, the casein 
may be separated by precipitating both with alcohol 
and boiling the precipitate, which coagulates the casein, 
rendering it insoluble. The precipitated glue may be 
then taken up with hot water. 

Egg- and Blood-Albumin. — Egg-albumin is usually 
translucent and of a pale yellow color. It should be 
free from blisters which are the evidence of imperfect 
coagulation. All commercial albumen of good quality 
should be free from any suggestion of the odors of 
putrefaction and unpleasant taste. On treatment with 
cold water and constant stirring, it should dissolve 
without leaving any residue. 

Albumin is frequently adulterated with gelatine, sugar, 
dextrine, and even flour. For its examination, Allen 


GLUE AND GELATINE SUBSTITUTES 83 


proposes the following method which has yielded the 
author uniformly successful results: 

Five grams of the powdered sample are treated 
with 50 c. c. of cold water and stirred frequently until 
all soluble matters are in solution. Pure samples leave 
no residue. A few drops of acetic acid are added and 
any insoluble residue filtered off through silk or fine 
muslin. This may consist of coagulated albumin, casein, 
starch, or membranous matter. The casein may be 
dissolved out by treatment with very dilute caustic 
soda and precipitated by exact neutralization with 
acetic acid. The aqueous solution of the sample is 
now boiled, when the albumin is thrown down as a 
flocculent precipitate which may be filtered off, washed, 
and weighed; or treated by Kjeldahl’s process and the 
albumin deduced from the ammonia obtained. “The 
filtrate from the albumin is treated with acetic acid 
and potassium ferrocyanide, to make sure that all the 
albumin has been precipitated. Any organic precipitate 
produced by this treatment will consist of casein. Zinc, 
which may have been added to increase the thickening 
power, will be thrown down at this juncture as white 
ferrocyanide. If no proteid remain in solution, gelatin 
may be precipitated by the addition of tannin, the 
liquid filtered and concentrated to small bulk, when any 
gum or dextrine will be precipitated by treatment with 
alcohol. Sugar, if present, will remain in solution with 
the aleohol and may be detected by boiling off the 
alcohol, heating the liquid with hydrochloric acid, and 
treating with Fehling’s solution. Sugar might also be 
extracted by treating the original dry sample with 
alcohol. 


84 GLUES AND GELATINE 


For the assay of commercial albumin, Ziegler dissolves 
20 grams of the sample in 100. ¢. cold water. The 
solution is strained through a sieve and 10 ¢. c. of the 
clarified solution is added to a boiling 20 per cent 
solution of alum. The appearance and volume of the 
coagulum is noted,‘and then it is washed, dried, and 
weighed. With pure albumin the results are very good 
and their accuracy is not affected by the presence of 
dextrine. Gum arabic, however, interferes seriously 
with the precipitation of the albumin. (De Koninck.) 

Blood- and egg-albumin may be distinguished from 
each other by the following reactions: 

Solutions of blood-albumin in which are present the 
ordinary salts are unaffected by agitation with ether, 
whereas egg-albumin is coagulated. If in dilute solu- 
tion’ the precipitate appears at the junction of the 
layers of ether and water. It is to be observed that if 
no salts are present this behavior is reversed, the blood- 


albumin being precipitated while the egg- remains — 


unaffected. 

Blood-albumin is readily soluble in concentrated nitric 
acid, while egg-albumin is only sparingly soluble in this 
medium. 

Dextrine Crystals. — The active constituent of dex- 
trines may be designated as dextrin. Chemically, this 
product is intermediate between starch and grape-sugar. 
Its empirical formula alone is known, and is (C,H,,0,),, 
that is, some multiple of the starch formula O©,H,,0,. 
If the process of dextrinization, 7.e., the treatment of 
a starch with a trace of nitric acid with the aid af heat, 
be prolonged, the starch is first converted into dextrin 
and subsequently into grape-sugar, C,H,,O,. The con- 


het 


ee) 2 


GLUE AND GELATINE SUBSTITUTES 85 


version of starch into dextrin, and, subsequently, of 
dextrin into grape-sugar, may therefore be assumed to 
be that of hydrolysis and may roughly be stated by the 
equation, 

C,.H,,0; is HO oe C,H0.. 


Commercial dextrine must be regarded as a mixture 
of unconverted starch, dextrin, and grape-sugar. The 
further conversion is carried, the more soluble the 
product, the deeper the shade of its solution, and the 
greater the quantity of grape-sugar present. Dex- 
trines are sometimes produced by the action of malt- 
infusion upon solutions of starch, the dvastase of the 
malt converting the starch first into dextrin and ulti- 
mately into the sugar, maltose. The temperature of 
the operation should never exceed 60° F. 

Both levulose and maltose reduce Fehling’s solution, 
and hence if the solution of agglutinant be suspected to 
be dextrine, this may readily be recognized. This test 
is applicable to the detection of ‘Liquid Glue” or 
Boston Gum, although the general appearance and char- 
acteristics of these serve to identify them in the majority 
of instances. 

Japanese Gelatine, etc. — These will be recognized by 
the form in which they appear in commerce, the long, 
slender strips resembling only a certain form of isinglass, 
and the difference in the characters of the jelly will 
soon differentiate them from the latter. 


CHAPTER V 


FOREIGN GLUES 


Comparison of Foreign and Domestic Glues. — A con- 
siderable proportion of the glue consumed annually in 
the United States is of foreign manufacture and, were 
not the tariff duty on these goods so high as to be 
almost prohibitive in many instances, it is to be feared 
that some grades would supplant the corresponding 
domestic in certain classes of work. The contention, 
advanced by many, that foreign glues are invariably 
productive of better results than the domestic goods of 
equal test-strength, is entirely too broad and sweeping. 
Yet it must be admitted that there are times when a 
well made 1% foreign glue will do the work of a poorly 
made 14 domestic. 

Much uncertainty exists in the minds of the glue- 
consuming public as to whether the vaunted superiority 
of foreign glue over our own product is founded on 
imagination or on fact. The radical difference in ap- 
pearance between foreign and domestic glues has its 
origin in the fact that the stock from which the former 
are made is selected with the greatest care. In addition 
it is frequently hand-picked, the laborious process of 
removing physical imperfections of the stock by hand 
being reckoned as nought compared with the possibility 
of producing an off-grade of glue through neglect of 

86 


FOREIGN GLUES 87 


this precaution. Labor conditions are such in England 
and on the Continent that it is possible to subject both 
stock and glue-liquor to operations precluded by the 
high cost of labor in the United States. Where the 
European manufacturer can avail himself, at a trifling 
cost, of the services of the aged and infirm of the locality 
in which his factory is situate, for the purpose of 
hand-picking glue-stock, the same labor would com- 
mand many times the price in the United States and 
hence the increased cost of production would speedily 
place beyond the pale of competition the manufacturer 
who sought to take advantage of such process. 

Factors other than the initial treatment of stock 
operate to create a difference between foreign and 
domestic glues. The glue-liquors are, as a rule, sub- 
jected to processes of clarification or those tending to 
precipitate the viscous, non-adhesive elements. For 
this reason, the majority of foreign glues are markedly 
translucent, if not actually transparent. The viscosity 
of their solutions is lower than the subsequent jelly- 
strength would indicate, as is the case with our acid- 
treated glues. 

It is to be borne in mind that glue is glue, the world 
over, and that the manufacturer, abroad, is subject to 
the same limitations in production as the manufac- 
turer in this country. The author is not in a position 
to state whether or not all European manufacturers 
sell their glue on test. If one is to judge from the 
contributions of foreign authors to the literature of 
the subject, each manufacturer employs an individual 
test-system which certainly must fail of enlightening 
him as to the commercial fitness of his product, deter- 


88 GLUES AND GELATINE 


mined by the requirement of the American consumer. 
This view is materially strengthened by applying the 
test to various makes and grades of imported glues, 
when the discrepancies in price between those of identi- 
cal strength and quality would indicate that the price is 
governed altogether by cost of production. A German 
manufacturer will frequently demand a price for a glue 
testing 1? for which price an English manufacturer will 
offer one of 14 test. Many other examples might be 
cited in confirmation of the theory that there is not a 
suggestion of test-uniformity among European manu- 
facturers. 

Save with the higher, more expensive grades, the 
boasted uniformity of foreign glues is largely a myth. 
For four years the author has tested regular monthly 
shipments from divers European factories, and there 
have been frequently variations corresponding to two 
domestic grades. Even the higher grades vary at times. 
It may be safely asserted that there is no economy in 
using a low-grade imported product in preference to a 
domestic. A foreign glue of 1% strength will usually 
cost from eight to nine cents per pound here, when 
the duty and freight have been added to the quoted 
price. A clever buyer will procure a domestic glue of at 
least 14 strength for the same money. 

In certain classes of work, however, particularly where 
the glue is to be worked in conjunction with unstable 
ehemicals, or for finishing delicate fabrics, the use of 
foreign glues is of material advantage, if not imperative. 
All substances tending to affect the chemicals have 
been removed through the initial treatment of the stock 
or the very processes of clarification or precipitation 


FOREIGN GLUES | 89 


before alluded to. Again, their viscosities being low 
as a result of these treatments, foreign glues are better 
adapted to sizing work than are many domestic grades. 

These exceptions granted, it is an open question 
whether foreign glues of all grades are more economical 
in actual work than the corresponding domestic grades. 
Personally, the writer thinks not. Certain domestic 
glues, those made by the Michigan Carbon Works, for 
example, are identical in appearance with some grades 
of foreign, for the reason that they are made in just 
the same way. As aresult, the price of these products 
is far higher than that of the regular domestic of 
the same grade. Thus, the 12 of this make commands 
a price averaging twelve cents per pound, for which 
could be obtained a straight hide 14 glue. The very 
fact that such glues are produced in this country bears 
out the contention that it is not owing to any superiority 
in skill, but rather to variance in the methods of treating 
the stock and liquors, that foreign manufacturers pro- 
duce an article so different in appearance and general 
working properties from American. 

Granting, further, the claim that the 13 glue of the 
above-mentioned make will do the work of the 14 hide 
obtainable for the same money, the latter is apt to 
prove much more uniform in the end. While clarifica- 
tion and other processes doubtless render the finished 
glue better for such purposes as sizing, these processes 
are apt to deprive the article of much valuable binding 
material in the endeavor to remove viscous, non-adhe- 
sive elements. While conceding the superiority of a 
foreign glue as compared with a domestic bone product 
of even greater strength, the author holds that if a care- 


90 GLUES AND GELATINE 


ful comparison be made between the average foreign 
and a domestic hide glue of equal strength, in actual 
work, the verdict will be in favor of the latter, as it is 
far cheaper and if properly applied will do as good 
work, if not better. Few, if any, foreign glues equal 
the domestic A Extras or even the 1 Extras. A foreign 
glue, testing 1 X, is worth in this market fourteen or 
fifteen cents per pound, a price which will procure a 
domestic A Extra superior in every way. 

It must not be inferred that all foreign glues are alike. 
While they have many characteristics in common, such 
as clearness and extreme hardness, they are in a measure 
distinguishable according to the country which produces 
them. The author’s experience with foreign glues has 
been limited to the examination of English, French, 
Italian, and German of a great variety of makes. The 
Italian and French correspond in general appearance 
and behavior. The majority of German are widely 
different from any other make, while the English may 
be regarded as most nearly corresponding with some of 
our domestic product. It would seem that to Russia 
belongs the credit of first producing opaque or colored 
glues, since glues of this class are designated Russian 
even though made in Germany or elsewhere. Similarly, 
much Scotch glue is manufactured in France, and a 
grade of Irish glue is produced in Lincolnshire, England. 
It is thus seen that some of these designations refer to 
particular brands of glue, rather than indicating the 
country producing them. 

The United States produces but little gelatine of 
good quality, the bulk of that consumed here being 
imported. Domestic gelatines lack the purity of the 


FOREIGN GLUES 91 


foreign product. They are rather too gluey, and are 
deficient in strength (water-absorbing quality). Ger- 
many and France lead in the production of gelatine 
applicable to the arts, while England has produced 
several edible varieties of great merit. French and 
Italian gelatines, as a rule, are stronger than German. 
That American manufacturers will, in the near future, 
produce goods of equal merit, is a certainty. Already 
the 00 and 000 gelatines of the Michigan Carbon Works 
are achieving prominence, while some of the Western 
packing-houses are producing gelatines of great strength. 
Although the products alluded to are fairly pure and 
strong there is considerable room for their improve- 
ment. 

Since foreign glues of every make exhibit certain 
characteristics in common, it is to be inferred that the 
higher grades owe their superiority to differences in 
stock rather than in methods of preparation and boiling. 
This contention is supported by the fact that at certain 
factories in the United States, glue-makers are employed 
whose experience and training have been mainly Euro- 
pean, and particularly, German. Asa result, the prod- 
uct of these factories is similar in appearance and 
working properties to foreign-made glue, and differs 
from it in that it is invariably two or three grades 
stronger. This added strength can be due only to the 
superiority of American stock. Thus, an Indiana fac- 
tory employing a German glue-maker produces a pale 
yellow ribbon glue well adapted to silk finishing and 
the preparation of gummed labels. This glue, which is 
identical with several varieties of German, so far as 
appearance is concerned, is far stronger than any 


92 GLUES AND GELATINE 


German glue that can be bought at the price (nine and 
one half cents) in this market. The other glues pro- 
duced at these works are characterized by the clearness 
of the foreign product with the strength of the average 
domestic hide glue. Such are superior to the corre- 
sponding imported grades in that they are better pre- 
served. ; 

On the other hand, differences characterizing domestic 
glues are due to variations of process as well as of 
stock. The problem of a proper stock supply is be- 
coming a serious one with many of our factories. 
The markets are closely watched by the representatives 
of many, and stock purchased in every quarter of the 
country. So great is the demand, that stock of inferior 
quality is frequently purchased and the skill of the 
glue-maker depended upon to produce a good article. 
This will account in large measure for the frequent 
variations in test of the same grade of glue. It is to be 
assumed that even a greater stringency exists abroad, 
where packing industries as well as tanning are not so 
extensive as in this country. Despite this, stock im- 
ported from Europe is at times offered in this market, 
while that coming from Argentina and other South 
American countries is commonly employed for glue 
making both here and abroad. Contrary to popular 
belief, stock is at as great a premium with the pack- 
ing-houses operating glue works as with the smaller 
producer. Since each department of such a concern is 
conducted as.a separate business, it is necessary for the 
glue department to purchase the stock from the other 
departments, with the result that it is frequently more 
profitable to buy in the open market. Ohio, Connecti- 


FOREIGN GLUES 93 


cut, and Massachusetts are almost inexhaustible sources 
of stock supply. Newark, N.J., a veritable center of 
the leather industry, furnishes considerable glue-stock, 
as do the isolated tanneries throughout the country. 

So varied is the stock in character, that it is possible 
for the American glue-maker, through individuality in 
treatment, to produce a characteristic and distinctive 
glue. Thus the Baeder Adamson, Armour, Swift, 
Cudahy, Nelson Morris, American Tanners, Delaney, 
Anglo-American, Cooper, and Delaware, product exhibit 
individual characteristics enabling the experienced to 
identify them with comparative ease. On the other 
hand, a brown medium-priced foreign glue might readily 
be the output of any one of a score of European fac- 
tories, for all that appearance or test tells. Given a spe- 
cific requirement, almost any imported glue of requisite 
strength will answer, whether made in Germany, France, 
England, or Italy. The same rule applies to imported 
gelatines, so similar are the corresponding grades 
produced by each country. 

It is well known that the modus operandi in almost 
every European industry is largely governed by tradi- 
tion. In an industry such as glue making, where the 
art is frequently transmitted from father to son, tradi- 
tion plays a most important part and its influence is to 
be observed even in this country in the manufacture of 
glue. It is to be inferred that, because of tradition, 
European glues will continue the same, time without 
end. The American trained glue-maker, though as a 
rule conservative, is more prone to experiment than is 
his European cousin; and since development of any 
industry is dependent upon experiment, glue making 


94 GLUES AND GELATINE 


in the United States will doubtless eventually be 
reduced to almost an exact science. 

Lack of space forbids the description of all the varie- 
ties of imported glue examined by the author, and 
hence discussion is limited to such as are typical. 

English Glues. — While exhibiting certain character- 
istics in common with those produced upon the Con- 
tinent, glues made in England differ somewhat and 
may be considered as intermediate. between domestic 
glues and those manufactured in Continental Europe. 
Whether this is due to differences in stock or in treat- 
ment is an open question. As it is, some English 
ground hide glues closely resemble our own higher 
grades, and certain ground bone glues of English manu- 
facture have their domestic prototypes in the C X glue 
of Armour & Co. and of other American factories. 

Probably the best known English glue in this market 
is the “Walsall.” This appears in the form of fairly 
thin sheets of good texture, brownish yellow in color 
and bearing the marks of the net. This may be regarded 
as the type of high-grade English glue and its merit is 
attested by the fact that it is extensively imitated. 
It is applied largely in the manufacture of matches and 
is also well adapted to joiner-work. 

A ground hide glue produced by the Grove Chemical 
& Fertilizer Works closely resembles American ground 
hide glues. This concern also manufactures weak bone 
glues very similar to our own, including a ‘‘ concentrated 
size powder,” which is regularly duplicated in this 
country under the less fantastic name of powdered bone 
glue. 

Other types of English glue are the Crown English, 


FOREIGN GLUES 95 


Crown No. 1, D. F., ete., made by Duche Freres who 
maintain extensive works both in England and in 
France. The “Star and Anchor” glue produced by 
this concern is typical of either French or English glues 
of a certain class. It finds an extensive use in this 
country, particularly in the manufacture of carriages, 
in which industry there exists a rabid prejudice in 
favor of foreign glues. 

Although some English glues are described by the 
makers as free from acid or alkali and even grease, such 
is not always the case. Some show at times as much as 
0.5 per cent mineral acidity and appreciable quantities 
of grease. These facts are not cited with a view to 
disparaging the product. It 1s a matter of extreme 
difficulty to produce a glue absolutely free from alkali, 
acid, or grease. Others, again, are remarkably beau- 
tiful in appearance but extremely weak, testing No. 2 
They are pale yellow sheets, very clear and transparent, 
with high luster. A working trial of these glues is 
fraught with extreme disappointment. It cannot be 
stated, with any degree of finality, that their lack of 
strength is due to the very processes that have con- 
tributed to their fine texture and appearance, but it is 
to be inferred that such is the case. 

_ Irish Glues. — Two grades of Irish glue are very well 
known in this market — the Block C. and the Block 
C. L. The former is made in Ireland, while the latter is 
produced in Lincolnshire England, as the initial, L, de- 
notes. Both are high-grade glues. The Block C. appears 
in the market in the form of broad, seal-brown sheets, 
cut fairly thin and prominently marked by the nets. It 
tests about 1 X on the average and, though considerably 


96 GLUES AND GELATINE 


clearer, is otherwise identical with a medium, thin-cut, 
domestic glue, made from straight hide. The Block 
C. L. is of a somewhat different shade and thicker cut. 
As a rule, it is very greasy, much more so than any 
foreign glue examined by the author. Both Block C. 
and Block C. L. are used in the manufacture of matches, 
and it is claimed by some that the grease of the latter 
renders it even more valuable than the former for this 
purpose. It would seem, however, that this grease is a 
serious defect in a glue intended for match-composition. 

There is a so-called Irish glue, designated ‘Irish, 
G. B.,” appearing in this market. It bears no resem- 
-blance to either of the foregoing grades and, in fact, is 
not Irish glue at all, being produced in England in an 
abortive endeavor to imitate the “Walsall” glue. A 
sample, figuring in a lawsuit, was examined by the 
author. It is in sheet form, very pale of color, and 
appears to be made largely from skin-stock. The 
sample was strongly alkaline in reaction and chromate 
of lead was present in the ash, resulting from the prob- 
able addition of a lead salt to impart factitious weight 
and a chromate to enhance the drying properties of the 
glue. 

Scotch Glue. — Several samples of this variety of glue 
have come to the writer’s notice, one made in England, 
another produced in France, and still another of German 
manufacture. Scotch glue is characterized by extreme 
darkness of color. Held away from the light, it appears 
to be almost black; but if held up to the light, the sheet 
is seen to be of a deep red or claret color. The glue is 
in the form of sheets, seven to eight inches square and 
about one-half inch thick. So tough is this glue, that 


FOREIGN GLUES 97 


sharp blows with a hammer are necessary to break it, 
and if one were to judge by the fracture alone, it would 
be considered of great strength. It seldom tests more 
than 1?, however, and more often 17 or No. 2. Scotch 
glue is of such thickness that it is necessary to soak it 
twenty-four hours before it will melt properly. Of the 
samples examined by the author, that of French man- 
ufacture was the best. This tested 1?, but owing to the 
peculiar character of foreign-made glues held a wood- 
joint so strongly that crushing blows with a hammer 
failed to separate the two pieces for some little, time. 
German Glues. — While Germany produces glues in 
far greater variety than other European countries, her 
product is, as a rule, inferior in quality. This is doubt- 
less due in part to differences in stock as well as in 
methods of manipulation. The fact remains, however, 
that despite the alluring superlatives employed in the 
description of the product on the printed labels attached 
to the sheets of each make, a large proportion of German 
glues is poorly made. It would seem that Germany 
excels in the manufacture of medium quality bone glues. 
The hide glues, or the mixed bone and hide, cannot 
compare with our own product either in strength or in 
keeping qualities. Those that are at all serviceable 
cost from seventeen to twenty cents per pound in this 
market — a price which is ridiculously high. 7 
As has been pointed out, the printed guarantees of 
the manufacturer are not always substantiated by test. 
German glues may be roughly divided into two classes, 
“Superior” and “Extra Superior,” and frequently the 
former are of better quality than the latter. To these 
adjectives there are added such as “‘Tett-frei”’ (grease- 


98 GLUES AND GELATINE 


free), ‘‘Sauer-frei” (acid-free), etc. The glue is also 
described either as “‘Leder Leim” (hide glue) or ‘‘ Kno- 
chen Leim”’ (bone glue). Many of those described as 
pure hide contain considerable bone liquor, and some 
described as acid- or alkali-free react strongly with litmus 
for one or the other of these conditions. 

German glues are usually in the form of sheets about 
five inches long by two wide. In thickness, these vary 
from a quarter to a half an inch. The poorer grades 
are usually very difficult of fracture, breaking in long 
splintery strips. The better varieties are not so thick 
cut. A chocolate brown is the prevailing color, although 
the higher grades range through the shades of yellow. 
Those that can be purchased in this market for seven 
or eight cents per pound seldom test over 1? and are 
more likely to test 1{ and No. 2. 

Cologne glue may be regarded as typical of the 
German product. Originally, this was a very fine 
article, but of late years has markedly deteriorated 
owing to extensive imitation in which the original glue 
formula has been entirely lost sight of. So superior 
was the quality of this glue and so general its recogni- 
tion that it has needed but the term ‘‘Cologne”’ to effect 
the speedy sale of many a spurious grade of glue. The 
genuine article is in the form of small, square cakes, 
very thick and extremely hard. It is manufactured 
from scraps of hide and skin, which, after liming, are 
bleached; and in order to obtain as clear a Jelly as 
possible, certain portions of the glue-stock are rejected 
after bleaching and worked into darker glue. The fact 
that the genuine is characterized by great clearness of 
jelly has led to its extensive imitation. Bone glues are 


FOREIGN GLUES 99 


frequently described and sold as Cologne glue, even by 
German manufacturers themselves, coming into the 
market as “‘Kolnische Knochen Leim.” Such charac- 
terization is in itself sufficient to warn the prospective 
purchaser that he is offered a spurious article. Bone 
glue is not true Cologne glue. 

Many of the cheaper grades of German glue lack the 
necessary keeping qualities to encourage their extensive 
use in this country. Even some of the higher grades 
are insufficiently preserved, while over-liming is fre- 
quently to be observed in both. This latter defect is 
noticeable chiefly in glues of great clearness and pale- 
ness of color, yielding very clear jellies, and is doubt- 
less due in many instances to the attempt to bleach 
the stock after liming through the agency of milk of 
lime. Pale yellow, clear, bone glues owe both clearness 
and color to treatment of the liquors with sulphurous 
acid gas. These glues, while very fine in appearance, 
are extremely weak in test. 

French Glues. — Glues of French manufacture are far 
stronger and better in quality than other European 
glues obtainable for the same price in this market. 
The lower grades are of great purity and test from one 
to two grades (Cooper) higher than the corresponding 
German or even English product. A peculiarity of 
French glues is that, save for the cheaper varieties, 
which are invariably dark in color, they occupy a posi- 
tion intermediate between glues and gelatines. Were 
they cut thinner, many of the medium grades would 
pass for low-quality gelatines. , 

The Jacquet Coignet glues are unquestionably the 
highest type of French product and, in a sense, of any 


100 GLUES AND GELATINE 


glues produced. ‘They embody the purity of the average 
commercial gelatine with all the strength and adhesive- 
ness of a high-class hide glue. A favorite grade, much 
used by representative cabinet-makers in this country, 
appears in sheets about eight inches square and a 
quarter of an inch thick, medium yellow in color. This 
tests, as a rule, 1 Extra, and is conceded to be without 
an equal in binding two pieces of wood. 

The glues and gelatines produced by Messrs. Tancrede 
& Cie. are more truly representative of the French 
product than the above, since the J. Coignet are of 
such merit as to place them beyond comparison with 
other makes without too great a disparagement of the 
latter. Several varieties of glue are produced by Tan- 
crede, the ‘‘Colle sans Marque,” “‘ Ecossais,’”’ “Soleil,” 
and ‘‘ Medaille.” 

The ‘Colle sans Marque”? (Unbranded glue) is the 
weakest of these glues, testing on an average 1{, although 
sometimes running as high as 1?. This variation in 
test is due to the fact that at times the glue is shipped 
fresher than at others. The color of this glue is dark 
brown and the sheets are from six to seven inches square. 
The ‘Ecossais” (Scotch glue) has already been de- 
scribed in the foregoing discussion of glues of this name. 
The “Soleil” (Sun) and ‘‘Medaille’” (Medal) glues are 
in broad sheets of a good yellow color, and fairly thick. 
They are clearer than the Unbranded and Scotch and 
exhibit “fiber” to a greater degree. By “fiber” is 
meant not only the appearance of strength, since this is 
common to a great number of glues, domestic as well as 
foreign, which prove very weak on test, but rather a 
“waviness” in the texture that is an infallible index of 


FOREIGN GLUES 101 


strength. Certain forms of cutting apparatus faintly 
mark the surface of the dried glue with parallel lines, 
very close together. These must not be mistaken for 
“fiber.” Just as the “grain” in wood indicates sound- 
ness as well as careful treatment, so the “fiber” in glue 
is indicative, not only of good stock, but proper treat- 
ment and cooking as well. The Sun and Medal glues 
average in test 14 and 1} respectively. A characteristic 
of these glues, worthy of notice, is that the viscosities 
of their solutions are not as low, proportionately to 
their jelly strengths, as those of the great number of 
foreign glues, although both of these glues are quite 
clear. It is evident, therefore, that this clearness has 
its origin in the preliminary treatment of the stock, 
rather than in processes aimed to remove by precipita- 
tion, the non-adhesive, viscous elements in the glue 
liquors. It has already been pointed out that such 
processes are too radical, removing much that is available 
in the proper working of the glue. 

Tancrede & Cie. produce a gelatine that is without 
exception the strongest that has come to the author’s 
notice. It is in narrow sheets of medium thickness, of 
a pale yellow color in some lights and almost colorless 
in others. The test is two grades higher than A Extra 
and seldom varies. The jelly of a 25 per cent solution, 
while yellowish and not absolutely clear, 1s so tough 
that it is with difficulty pulled to pieces with the fingers. 
The melting-point of the jelly is rather too high for a 
culinary article. The solution is decidedly alkaline in 
reaction and its viscosity averages 35 seconds. The 
objection is made that this gelatine is in reality too 
strong for the average work. Despite its peculiar 


102 GLUES AND GELATINE 
characteristics, it is a true gelatine, the addition of even 
a few drops of 40 per cent formaldehyde solution pro- 
ducing a change to a tough, elastic mass. In the 
matter of absorbing foreign odors, it 1s as sensitive as 
butter, and if stored for a short time in proximity of 
crude phenol will soon become impregnated with the 
permeating odor of the latter. This fact has led to the 
erroneous conjecture that the product itself is preserved 
by means of carbolic acid and hence manifestly unfit 
for culinary applications. 

Italian Glues. — While comparatively little glue is 
produced in Italy, as compared with the output of 
other countries, the product is of excellent quality, and 
in many respects similar to the French, being typical 
of ‘‘gelatine-glue”’ to even a greater degree than the 
latter product. Two concerns, the ‘‘Societa Agricola, 
etc.,’ in Milan, and the “Fabrici Torinese di Colla e 
Cocimo,” in Sorrento, produce glues that are worthy of 
attention. The Societa glue is a cheap grade similar’ 
to the Colle sans Marque of Tancrede, testing about the 
same, but somewhat better adapted to sizing work. 
This corresponds, also, with certain of the weaker 
English glues, but is vastly superior to the low-grade 
German. The Fabrici produces gelatine-glues and gela- 
tines, the former having their exact duplicates in the 
product of the Michigan Carbon Works, and the latter 
in the Silver Label, Bronze Label, and Gold Label 
gelatines of German manufacture. Like the German 
product, the Torinese high-grade gelatines are in the 
form of colorless, extremely thin, transparent sheets, 
testing from 14 to 1 X. The jellies are remarkably 
clear and of proper melting-point. Italian glues are a 


FOREIGN GLUES 103 


trifle higher in price than the corresponding French, as 
they are redipped after drying the first time, in order to 
improve the gloss or luster. 

Russian Glue. — From what has been said in regard 
to Russia as the originator of opaque or colored glues, 
it must not be inferred that opacity is achieved in 
exactly the same way as in this country. A consider- 
able quantity of Russian glue is made from bones, the 
dry product being in the form of brownish-white sheets. 
The bones are degreased by the usual method, and the 
customary treatment with hydrochloric acid resorted 
to, to deprive them of mineral constituents. The acid is 
permitted to act on the bones until they just become 
flexible, when the acid is drawn off. As a result of this 
incomplete treatment, phosphates remain in the carti- 
lage and are incorporated with the finished product 
which thereby acquires a whitish color. The practice 
of adding mineral coloring matters to both hide and 
bone glues originated in the endeavor to imitate Rus- 
sian glue. It is said that the addition of a small amount 
of coloring matter does not affect the tenacity of glue, 
but that an excess tends to weaken it. This does not 
accord with the contention of numerous consumers of 
opaque or colored glues that such product is stronger 
and dries quicker than the corresponding clear. 

Some of the opaque or colored glues manufactured in 
various European countries are genuine Russian, pre- 
pared by the above process. Others, again, are made 
by the same methods as are in vogue in this country, 
namely, the addition to the glue liquors of various 
- mineral coloring matters... 


CHAPTER VI 


SELECTION OF GLUE FOR VARIOUS INDUSTRIES | 


Preliminary Considerations. — While no definite rule 
can be enunciated relative to the selection of a glue for 
a specific usage, attention must be paid to certain 
fundamental considerations. Experience is the safest 
and surest guide in glue selection; but experience, with 
glue, is to be acquired only at great pains and expense. 
Hence the necessity of applying the dicta of common 
sense to the selection of an article that will answer the 
requirement of the consumer. It is manifest that 
stronger glues are required for some purposes than for 
others, and that common bone glues will not do the 
work of high-grade hide. It is to be regretted that the 
average consumer, in selecting glue, is influenced alto- 
gether by the question of price. While strenuous com- 
petition in all branches of manufacture renders it 
imperative that raw material be purchased as cheaply 
as possible, where glues are concerned too little atten- 
tion is paid to the quality of the material. 

Through a lamentable ignorance of its properties and, 
more particularly, through ignorance of proper methods 
of application, many a good glue is condemned and 
frequently an inferior article, at even higher price, 
substituted. Through this same misconception of the 
nature and properties of glue, an article is oft chosen 

104 


SELECTION OF GLUES 105 


that is unfit for the particular requirement. The aver- 
age consumer proceeds upon the basis that he does not 
wish to pay more than, let us say, eight cents per pound 
for the glue, regardless whether the proper glue for his 
work can be purchased for the money. Utterly failing 
to consider that a glue at twelve cents is often far cheaper 
in actual work than one at eight, he tries every make 
of glue that is offered him at the latter cost and even- 
tually clings to that furnishing the best results. His 
supply of this cut off, he is at sea regarding further 
selection, and it is highly probable that he is never 
successful in obtaining the glue best fitted for his work. 

Glues that exhibit palpable defects of stock or manip- 
ulation are unfit for any purpose. ‘True, they can be 
used; but the results will never be entirely satisfactory. 
As has been previously emphasized, the consumer’s only 
path to safety, no matter for what purpose the glue is 
intended, lies in the test. It is only through continued 
testing that he can learn to distinguish glues and arrive 
at that state of enlightenment that will enable him to 
select the glue best adapted to his requirement, inde- 
pendent of any and all suggestions on the part of the 
dealer or manufacturer. Further, in this way alone 
will he be able to select the proper glue and. at the 
same time protect himself in the matter of price. 

Glues for Joiner-Work. — Prior to entering into the 
discussion of the relative merits of different makes of 
glue for joining wood, certain axiomatic principles may 
be enunciated in reference to the method of applying 
the glue. These once understood, it is not a matter of 
ereat difficulty to obtain a good glue for the work, at a 
satisfactory price. 


106 GLUES AND GELATINE 


1. Glue exerts a far greater hold on surfaces of wood that have 
been cut across the grain than on those that have been 
split, or cut with the grain. 

2. When two surfaces of split wood are laid together, the hold 
of the glue is the same whether the fibers are laid parallel 
or crosswise to one another. 

3. The value of a wood joint is dependent upon the union of the 
glue with the fiber of the wood. For glue to be properly 
effective, it must penetrate the pores of the wood; and the 
greater this penetration, the more substantial the joint. 

4. All other factors being equal, glues that dry slowly are in- 
variably stronger in the joint than those that dry rapidly. 

5. Except in the case of veneering, both surfaces of the wood 
should be. properly glued before junction. 

6. Do not use thick solutions of glue for joint-work. They con- 
geal too quickly, and hence fail to penetrate the pores of 
the wood, yielding, as a result, a weak joint. In every case, 
the glue must be worked well into the wood with a brush, 
much in the same manner as a coat of paint is applied. 

7. If glue is applied to hot wood, all the water of the glue solu- 
tion will be absorbed by the wood, leaving a thin inadhe- 
sive coating of glue at the surface of the joint, which, if 
made in this fashion, will hold only a limited time. 


In the fact that thin solutions of glue produce far 
stronger joints than thick, we find some basis for the 
contention that foreign glues are superior to domestic 
for this class of work. Given two solutions, of equal 
concentration, one of foreign glue and the other of 
domestic, both glues testing alike, the foreign glue will 
make the stronger joint for the reason that the vis- 
cosity of its solution, owing to clarification, is compara- 
tively lower than that of the domestic glue, and hence 
penetrates the wood with greater ease. Too much of 
the domestic glue will lie at the surface of the joint, and 
hence, despite the fact that it is as strong as the foreign, 
will not make so strong a joint. 

On the other hand, if the comparison be made be- 


SELECTION OF GLUES 107 


tween a foreign and a domestic glue of equal price, the 
verdict will be in favor of the domestic, inasmuch as a 
far stronger domestic product can be purchased for a 
given price. If, now, the domestic glue be brought 
into solution of viscosity equal to that of the solution 
of foreign glue, it wili be found that the jelly strength 
of this dilution is practically equal to that of the undi- 
luted solution of foreign glue. As a practical example, 
let us assume that the glues under discussion are a 
foreign and a domestic, each costing ten cents per 
pound. ‘The test of the foreign product is apt to be no 
higher than 1?, whereas that of a domestic glue purchas- 
able for this price is likely to be 12. Assuming, further, 
that in the preparation of the working solution, one 
pound of the foreign glue is dissolved in two pounds of 
water, since the domestic glue tests three grades stronger, 
to make a solution of this equal in viscosity and jelly 
strength to that of the foreign glue, it is possible to 
dissolve the domestic product, one pound in three and 
one half of water. Such solution will equal in pene- 
trating power and binding strength the solution of 
foreign glue; and it is readily seen that it costs fully 
one cent less per pound solution. This must not be 
construed as applying equally to all domestic glues. 
It is not to be expected that glue made from junk bone 
will answer as well as hide glue for binding wood. On 
the other hand, a well made acid-treated bone glue, if 
properly applied, will make a very strong joint. 

Since the sine qua non of a good glue for joint-work 
is that its solution shall properly penetrate the wood, 
it is important that the cabinet-maker test the viscosity 
as well as the strength of the glues submitted, before 


108 GLUES AND GELATINE 


making a selection. While it makes but little differ- 
ence, for this class of work, whether a glue is alkaline 
or acid, those exhibiting either of these conditions to 
excess should be rejected. A glue that has been pre- 
pared from over-limed stock (the evidence of which 
defect is extreme alkalinity), is manifestly unfit for 
joint-work. Such a glue is constantly weakening, even 
in the original dry state, and needs but to be brought 
into solution to promote rapid decomposition. The 
weakening and decomposition will proceed gradually 
after the glue has dried in the joint, and the joint in 
this way gradually weakens. Extreme alkalinity is not 
always evidence of over-liming; but if this be attended 
by abnormal viscosity, together with a tendency to 
foam, the glue-stock has suffered over-liming. A 
strongly acid glue is likely to have an effect on the 
wood itself, the fiber slowly yielding to the solvent 
action of the acid. 

Of equal importance to the considerations of acidity 
and alkalinity of cabinet glues is the question whether 
the glue has an abnormally high viscosity owing to 
solution of soaps, alum, etc. Alum-clarified or alum- 
thickened glues are always to be regarded with sus- 
picion, for, despite the clearness of their solutions, the 
viscosity is very high in proportion to the jelly strength. 
It is obvious that, in order to prepare a solution of such 
glue that will properly penetrate the wood, the solution 
becomes so dilute as to be radically deficient in glue 
strength, consisting largely of the salts that are im- 
parting factitious viscosity to the solution. Similarly, 
hide glues, with solutions of high viscosity owing to 
the presence of mucin or soaps, are to be rejected for 


SELECTION OF GLUES 109 


the same reason. In this connection, glues prepared 
from rabbit skins may be cited as typical of very strong 
glues that are unfit for joint work. Despite the fact 
that these seldom test lower than A Extra, the viscosity 
of their solution is abnormally high, owing to peculiar 
methods of treatment. The dilution necessary to insure 
proper penetration of the wood renders the glue very 
weak. ‘These glues may always be recognized by their 
peculiar rabbity odor, coupled with great clearness of 
both dry piece and solution, the latter being very thick 
owing to presence of alum. Some straight sheep glues, 
clarified by means of alum, are equally unfit for this 
class of work. 

That domestic glues, of good strength, answer equally 
as well as foreign for joint-work is evidenced by the 
fact that many cabinet-makers use the former exclu- 
sively. No glue consumer is more conservative and 
particular than the manufacturer of pianos, who fre- 
quently uses several grades of glue, both ground and 
flake. Some piano-makers will employ none but im- 
ported glues; others, again, none but colored and opaque 
domestic hide glues. No definite data as to the relative 
superiority of foreign or domestic glues can be obtained 
from a review of the opinions expressed by individual 
manufacturers of. cabinet work. In the selection of 
glue for almost every purpose, custom is the controlling 
factor. Through long and continued use, the consumer 
becomes accustomed to some particular brand of glue. 
He has learned its limitations as well as its merits, and 
hesitates to make a change, even though such change 
might result in a material saving of money, or the 
procural of a superior article for the same price he is 


110 GLUES AND GELATINE 


accustomed to pay, which is an equal saving. While 
there is considerable justification in the contention of 
the intelligent cabinet-maker, that one cannot say posi- 
tively how a glue is going to work until actually tried 
and the test of time applied, much unnecessary expense 
may be avoided by a rational preliminary test. It is 
not sufficient that jelly-strength alone be roughly 
assayed by noting the ‘‘water-taking” properties of 
the glue. As has been pointed out, the viscosity of the 
glue solution is of equal importance. By properly test- 
ing the glues submitted for his inspection, the consumer 
will at once be able to distinguish them in a practical 
way; and, having rejected those manifestly unfit, he 
may then subject the balance to the test of actual work, 
confident at least that no work will be harmed through 
their use, even though they do not supply results of 
maximum efficiency. 

In the manufacture of carriages, imported glues are 
used almost exclusively, the Star & Anchor being a 
favorite grade. Long habit in use is responsible for 
this, as there can be no question but that some domestic 
grades will work equally well. We must account for 
this so-called conservatism in the use of glue, in the 
absence, heretofore, of a reliable system of preliminary 
test. Having obtained satisfactory results from some 
one particular grade, it is but natural that the consumer 
should hesitate to change lest much valuable finished 
material be damaged. ‘This “conservatism,’’ however, 
is responsible for much useless expenditure. 

Glues for Wall Paper. — In the manufacture of wall 
papers, glue is employed for applying the clay, paris- 
white, etc., with which the papers are ‘‘grounded,” as 


SELECTION OF GLUES 111 


well as the sizing medium for the ground colors. In 
some instances the top colors are applied with glue, 
although it is commoner practice to use dextrine or 
“‘color-size”’ for this purpose. In no other industry 
_ has the search for an available substitute for glue been 
so rigorously prosecuted as in wall paper manufacture. 
Keen competition, resulting in the production of quan- 
tities of papers, selling for a few cents per roll, some 
printed in as many as twelve colors, with mica and 
bronze effects, has rendered imperative the purchase 
of raw material, of which glue is an important part, 
at rock-bottom cost. Casein is the only available glue 
substitute for the heavier work, and has been success- 
fully employed in times of glue scarcity and consequent 
prohibitive price. Sizes made by partially saponifying 
rosin with caustic alkali, and combining the emulsion 
with some starch such as tapioca or sago, have been 
tried without success. Their failure is due to the same 
causes that preclude the proper working of a number 
of glues, 2.e., they do not work uniformly with all pulp 
colors, causing a number to “liver.” Thus, a sizing 
compound that may work with reds, greens, and blues 
may fail utterly with yellows and blacks. 

In the selection of the proper glue for sizing the colors, 
much depends upon the colors themselves. Even the 
best of these are not always perfect, and the trouble 
arising from imperfectly or improperly sized colors is 
too frequently ascribed to imperfections of the glue. 
The same applies to difficulty arising from lack of 
union between the clay and glue, in the application of 
erounds. Difficulties of manipulation experienced at 
one factory will not obtain at another, for the reason 


112 GLUES AND GELATINE 


that some manufacturers turn out only a very cheap 
line of papers, while others produce none but high- 
grade. Itis at the works of the former that the greatest 
and most frequent difficulty is experienced, Inasmuch as 
only the cheapest raw material is purchased, and cheap 
pulp-colors, for example, are extremely troublesome. 
The importance of the relation between glue, on the 
one hand, and the colors, on the other, can best be 
understood from a limited exposition of the methods of 
manufacture of the latter. In order that the colors 
shall be at ail serviceable in the manufacture of wall 
paper, they must be in the insoluble or lake form. 
Otherwise, unless they were sized to such an extent 
that the mixture would consist of much glue and little — 
color, the latter would “bleed” or spread through the 
paper and over its surface. Again, it is not sufficient 
that these colors be lakes, for, were they supplied in 
the dry state, it would be necessary to incorporate them 
mechanically with water, before they could be mixed 
with the glue solution;.and this would necessitate the 
installation of mixing machinery at the wall paper plant, 
in order that the mixture should be uniform and not 
eritty. Accordingly, the aniline or coal-tar color, and, 
in some instances, natural dye-stuffs, are precipitated 
from aqueous solution upon an insoluble base such as 
finely divided barytes. The precipitated mass is settled 
and, after the supernatant fluid is withdrawn, is washed 
several times to free it from excess of precipitant or un- 
precipitated color. The mass is then conducted to the 
filter press and much of the moisture pressed out, or 
else this is gotten rid of by means of a centrifugal 
hydro-extractor. The resultant color is in the form of 


SELECTION OF GLUES 113 


a heavy paste or pulp, and in this state is readily and 
uniformly sized with glue solutions. Exposed to the 
air, the pulp colors dry out and may be triturated to 
an insoluble dry powder, which is difficult of uniform 
incorporation with water. 

Pulp-colors may roughly be divided into two classes — 
those that are made by first suspending the dry mineral 
base in the solution of color prior to precipitating the 
latter, and those that are prepared by precipitating the 
base simultaneously with the color. The former are 
poorer in quality and are frequently deficient in color 
_ strength. The latter cost more to prepare, but are 
productive of far better results. As an example of each 
class, the following formule of preparation may be 
cited. Lemon yellow, a color much used in printing 
wall papers, either direct or as a reducing agent for 
other colors, may be made by precipitating a solution 
of bichromate of potassium with one of lead acetate 
(sugar of lead). If a quantity of barytes or other — 
suitable, mineral base be suspended in the bichromate 
solution prior to the addition of the lead acetate, the 
chromate of lead will be precipitated upon the barytes 
and a pulp-color, of a sort, will result. In order that 
the whiteness of the base shall be fully hidden as well 
as that the resultant yellow shall be adequately strong, 
very concentrated solutions both of bichromate and 
acetate are required. The resultant precipitate will not 
stand much washing, as the color is not absolutely fixed 
upon the base. . 

Contrast with the above the pulp colors prepared 
from Ponceaux and Bordeaux reds, nigrosines, eosines, 
etc., in the following way. Four solutions are prepared, 


114 GLUES AND GELATINE 


one of calcined soda ash (carbonate of sodium), one 
of barium chloride, one of magnesium chloride, and one 
of caustic soda. The color to be precipitated is sepa- 
rately dissolved in water, the amount of color used 
being subject to the shade desired; and to this solution 
of color is added a proportion of the above in the order 
in which they are named. The carbonate of soda does 
not affect the color, but the barium chloride precipitates 
it and at the same time reacts with the sodium carbo- 
nate to form insoluble carbonate of barium. Similarly, 
the caustic soda and magnesium chloride react to form 
insoluble hydroxide of magnesia. The insoluble basic 
precipitates, being formed simultaneously with that of 
the color itself, are more finely divided than if corre- 
sponding quantities of barium carbonate and magne- 
sium hydrate had first been mechanically suspended 
in the color solution, and the color precipitated upon 
them by means of barium chloride. Again, the 
amended procedure insures the intimate incorporation 
of precipitated color and bases, which it is otherwise 
practically impossible to obtain. 

This digression from the subject in hand to that of 
pulp-color manufacture is deemed necessary in order 
that the working of different glues with different colors 
may be fully understood. Since so many ingredients 
enter into the composition of a pulp-color, and the 
cheaper are poorly fabricated, often containing an ex- 
cess of precipitant, from what has been said in 
previous chapters as to the effect of divers chemical 
reagents upon glue, it is of the greatest importance that 
the colors be free of all material tending to react with 
the glue used for sizing them. Conversely, it is of equal 


SELECTION OF GLUES 115 


importance that the glue be free of substances that may 
react with any excess of precipitant in the colors. Far 
oreater latitude is to be exercised in the selection of 
the glue for sizing, than of the colors to be sized. A 
given shade of color may be obtainable only through 
the use of certain chemicals, and since this shade may 
be essential to the requirement, it becomes necessary to 
adapt the glue to the color and not the color to the 
glue. For example, it is difficult to prepare Prussian 
blue lakes that are not greenish, and their manufacture 
involves the use of a number of chemicals without 
which the desired shade could not be achieved. De- 
spite the fact that such colors are known to be exces- 
sively over-loaded, the wall-paper manufacturer has no 
alternative save to use this color and find a glue that 
will work properly with it. 

To return to the colors themselves. Since these must 
cost as little as possible, the manufacturer of them is 
under necessity of selecting, for the base, such materials 
as are cheap and heavy. A definite quantity of color 
is required to produce a given shade, and the color must 
be of good quality. Hence there is no opportunity of 
reducing the cost at this end. Therefore, if the color 
maker is to produce an article of standard shade at low 
cost, and still make a profit, he must make his colors 
as heavy as possible. How this is accomplished will 
be readily seen from the following practical formulas: 

1. Eostnre Laker (TO MAKE 1260 LBs.) 


136 lbs. Soda ash. 
200 ‘ Sulphate of alumina. 
350 “ Chloride of barium. 
100 ‘ Lead acetate. 

75 ‘* Kosine. 


116 GLUES AND GELATINE 


Exclusive of eosine, the above costs about $1.80 per 
100 pounds. 


2. BREMEN BLUE (TO MAKE 750 LBS.) 


136 lbs. Soda ash. 
200 ‘“ Sulphate of alumina. 
350 ‘ Chloride of barium. 


50 “ Barytes. 
5.“ Malachite green. 
8 “ Tannic acid. 


Exclusive of colors and tannic acid, this eosts about 
$1.70 per 100 pounds. 


3. Turkey Rep (To MAKE 700 LBS.) 


75 lbs. Soda ash. 
150 ‘‘ Sulphate of alumina. 
210 ‘“‘ Chloride of barium. 


200 ‘‘ Barytes. 
30 “ Scarlet. 
30 “ Orange. 


Cost of the above, exclusive of colors, $1.40 per 100 


pounds, 
4. Maroon (Tro MAKE 1800 LBs.) 


150 lbs. Soda ash. 
300 ‘‘ Sulphate of alumina, 
420 ‘ Chloride of barium. 


10 “ Soap. 
300 ‘ Barytes. 
80 “ Scarlet. 
14 “ Fuchsine (magenta). 


Cost of the above, exclusive of colors, about $1.10 
per 100 pounds. 

The difference between the sum of the constituent 
weights and total product, in all of the above, is water. 
These may all be somewhat cheapened by the substitu- 


SELECTION OF GLUES De 


tion of calcium chloride of good strength for the chloride 
of barium. 

It is now seen that the constitution of the average 
pulp-color is far more complex than its appearance 
would indicate, and is anything but the simple result of 
precipitating the color upon a single insoluble base. It 
is obvious that where so many widely divergent chem- 
icals enter into the constitution of a product, and where, 
particularly, their proper inter-reaction is dependent 
upon certain mechanical or physical factors, it is highly 
probable that they will contain an excess of one or more 
materials that will either affect the glue or be affected 
by some substance which it contains. In the case of 
Bremen blue, for example, if there be any excess of 
tannic acid, it is not difficult to forecast what will occur 
when this is brought into conjunction with the glue 
solution. The insoluble, stringy precipitate of tannate 
of gelatin, even though small in amount, will be sufficient 
to “liver” the sized mass. In the case of the maroon, 
the presence of soap may or may not prove detrimental. 
This will depend upon what kind of soap is used. 

Since the colors, as such, must be accepted and used, 
the glues for wall paper must be chosen with a view to 
their possible effect upon the colors, rather than of the 
possible effect of the colors upon the glue. The glue 
may be neutral or it may be acid or alkaline. How will 
either of these latter conditions affect the colors in use? 
The careful examination of the glue for foam is neces- - 
‘sary, not only because of the mechanical difficulties that 
may arise from this cause, but also to determine if the 
cause of the foam is some glue substance that will 
affect the colors. Grease, in excess, unfits a glue for 


118 GLUES AND GELATINE 


wall-paper work, but not for the usually accepted 
reason. The ash of the glue revealing chemical salts, 
the query follows, are these present in sufficient quan- 
tity to react to disadvantage with the colors? Each of 
these contingencies is worthy of individual consideration. 

Acidity and Alkalinity. — Were the glue employed for 
sizing gold or aluminium bronzes, the question of acidity 
or alkalinity would be entitled to greater consideration 
than it is. The moderate amount of alkali or acid 
present in glue is not apt to affect the colors so far as 
changing the shade is concerned. Once precipitated, 
colors are not so susceptible to the action of acid and 
alkali as before precipitation. The chemist has only to 
view either. of these conditions from the standpoint of 
their possible reaction with substances present in the 
colors; and, save within the limits previously defined, 
viz., acidity or alkalinity in excess due to defects of 
manipulation, these may be disregarded. 

Grease. — A popular superstition exists among wall- 
paper manufacturers, to the effect that greasy glues 
are to be avoided because of the likelihood of their 
making grease spots in the paper. That this belief is 
without foundation is evidenced by the fact that for 
many years the Baeder, Adamson B4, a markedly 
greasy glue, was the favorite brand for wall-paper use. 
It is common practice, even at the best plants, whenever 
trouble arises through the foaming of glue and clay, or 
glue and colors, to “kill” the foam by the addition of 
lard oil, or grease and soda emulsions, to the mass. If 
the addition of grease itself, in this way, does not result 
in the formation of grease spots, it is to be assumed 
that the grease in the average glue never will. An 


SELECTION OF GLUES 119 


excess of grease in a wall-paper glue is to be avoided 
chiefly on account of its possible action with the colors. 
While, on the one hand, grease does much to prevent 
foam, and very frequently has a brightening effect upon 
the printed colors, on the other there is always the 
possibility that there are substances in the colors which 
will convert the grease into insoluble metallic soaps 
which will certainly interfere with the uniform flow of 
the sized colors from the printing machine. 

In applying the test for grease in the wall-paper 
factory, it is advisable to use the ungrounded hanging 
stock itself for the purpose, and to incorporate the 
glue solution to be tested with a standard pulp-color. 
In this way, a glue that might exhibit considerable 
grease if painted out with a plain aniline color, will in 
all probability exhibit none at all when a pulp-color is 
used, as the porous base of the color will absorb it. 
If, on such test, no grease permeates either color or 
paper, the glue is not too greasy for use; and it may be 
added that a glue that fails to qualify under this test 
is rarely to be found. Unless it 1s known that the 
colors contain excesses of material that will be affected 
by the grease, or affect it, it is wiser to choose a greasy 
glue in preference to a grease-free, as the grease will 
promote uniformity in the flow of the color from the 
roller of the printing machine. Many patent sizings 
are characterized by the addition of soap to the glue 
and base, as the former promotes the “‘slip”’ of the size. 
Grease itself will act in much the same way, and is so 
rapidly absorbed by the porous bases of the colors that 
it cannot interfere radically with the drying of the 
printed colors. 


120 GLUES AND GELATINE 


Foam in Wall-Paper Glues. — ‘The same considera- 
tions limiting the acid, alkali, or grease in wall-paper 
glues apply to the presence of foam. When trouble 
arises from this source, it is well to investigate the 
colors, rather than the glue, unless the latter, on pre- 
liminary test, was found to be foamy of itself, in which 
case it should never have been selected for the work. 
The chemist at the wall-paper factory will do well to 
observe the following, in testing glue, apart from deter- 
mining viscosity and jelly strength. If the glue reacts 
strongly alkaline with litmus—and by this is meant, 
if it turns the litmus a very deep blue —the glue should 
at once be tested for foam, and if found to be foamy 
-should be rejected without further examination. If the 
glue be only shghtly or moderately akaline, the foam 
test may be relegated to its proper place in the general 
test scheme. Extreme alkalinity points to over-liming, 
which means that the glue will foam badly in solution 
and also that it contains mucin and soaps which will 
not affiliate with the colors or clay. In certain quarters 
there exists a prejudice in favor of alkaline glues, based 
upon the assumption that the alkali brightens the colors. 
The contention has its origin in the fact that prepara- 
tions like “‘Tenacetine,”’ which are powerfully alkaline 
solutions of starches, certainly. brighten the printed 
colors to some extent. Such preparations are advocated 
_ for use in conjunction with the glue solution for sizing 
the colors, it being claimed that they increase the 
tenacity of the mass so sized. What has been said in 
previous pages in regard to glue substitutes applies 
equally to these preparations. 

Viscosity of Wall-Paper Glues. —In the selection of 


SELECTION OF GLUES 121 


wall-paper glues, certain mechanical considerations claim 
attention. Since the sized colors are applied from a 
roller, or, in the case of hand-printed papers, from a 
block bearing the design, the flow of the glue solution 
is a factor of considerable importance. The lower the 
viscosity of its solution, the better is a glue adapted to 
sizing work. Wall-paper manufacturers usually employ 
two grades of glue, one comparatively cheap and used 
_with the clay, etc., and the other of better quality, as 
it is used for sizing the chief colors. The latter is 
usually from three to four grades stronger than the 
former, which is, as a rule, a bone glue, but in some 
instances a hide, like the better quality. The strength 
of these is of less importance than their facility of flow 
and surface-covering qualities. True, the stronger these 
are, independent of abnormal viscosity, the more 
economical in use, for the same reasons applying to 
cabinet glues. 

In connection with the sizing of pulp-colors, we have 
again to compare the relative adaptability of foreign 
and domestic glues to a particular requirement. Foreign 
glues work exceptionally well in wall-paper work, as 
the viscosity of their solutions is such that they flow 
with the utmost readiness. Their serviceability is en- 
hanced by the fact that, owing to clarification, nearly 
all those substances tending to affect or to be affected 
by the colors have been removed. Despite this, com- 
paratively little straight foreign glue is used by Amer- 
ican wall-paper manufacturers. Some avail themselves 
of acid-treated bone glues which answer equally as well 
as the imported. Save such as employ a chemist to 
examine the raw material purchased, the majority have 


122 GLUES AND GELATINE 


not the slightest idea what kind of glue they are buying, 
and the purchasing department bases its verdict upon 
the opinions of the color mixers. It is obvious that 
colors will not show to equal advantage, if printed with 
a cloudy glue, to those printed with clear. Hence it 
is to the interest of the manufacturer to. use clarified 
clues. These, however, must be carefully selected and 
examined, for the reasons enumerated above. 

In the general testing of wall-paper glues, those with 
abnormally high viscosities must be rejected, as this 
peculiarity is due to the presence of substances that 
will react to disadvantage with the colors. Preferably 
those glues which, in solution, display viscosities dis- 
proportionately low to the jelly strength should be 
selected. These will give the best results with colors. 

The bulk of glue consumed in the wall-paper factory 
is in the ground form. In no other class of work is 
thorough and rapid solution of the glue so to be desired. 
Apart from facility in use, ground glues are of advantage 
in that two or more grades may be so mixed as to 
produce a glue fully answering all requirements as to 
flow and strength. 

Attention is directed to the futility of “‘testing”’ glues 
by determining the specific gravity of solutions of equal 
concentration, the measurement being effected by means 
of a hydrometer. This practice is altogether too preva- 
lent in our wall-paper factories. The same factors that 
unduly increase the viscosity, such as soaps, mucin, 
alum, etc., will increase the specific gravity, and hence 
this, per se, is as little indication of glue strength as 1s 
viscosity. Intelligently applied, the specific gravity 
test may be substituted for the determination of vis- 


SELECTION OF GLUES 123 


cosity. Its intelligent application, however, presup- 
poses a thorough acquaintance with the viscosity test; 
and, as the latter is but little more complicated, its use 
is to be recommended. 

To recapitulate, good wall-paper glue should be of 
adequate tensile strength, 13 for the grounds, and at 
least 13 for the colors. The glue to be used with the 
clay and in the coarser work should preferably be an 
acid-treated one, provided this is not too acid in re- 
action. Some clays are in a measure disintegrated by 
excesses of acid or alkali in the glue. This may or may 
not cause foaming of the mixture, but is sure to make it 
lumpy. The viscosity of the glue destined for the work 
must be normal or sub-normal. Not more than traces 
of mucin, soaps, and foreign salts must be present. 
Glues that are slightly colored work to advantage with 
the grounds. They do not work so well with delicate 
colors where clearness is desired. 

Glues for Surface-Coated Papers. — Much, if not all, of 
the foregoing is applicable to the selection of glues for 
surface-coated or glazed papers. It does not follow, 
however, that any glue adapted to wall-paper work 
will answer this particular requirement. Exceptions, 
due to a difference in the result to be obtained, must be 
considered. Thus, the glue employed in this work must, 
as a rule, be clearer than that used for wall paper, for 
not only is a high gloss in connection with the color 
required, but more glue is used in sizing the colors. 
Hence any cloudiness of the glue is apt to result in 
dulness of the coated paper. Again, the glue must be 
fairly strong, corresponding to the better grade em- 
ployed by the wall-paper manufacturer. It suffices the 


124 GLUES AND GELATINE 


latter if the sized color, when dry, yields but a little 
when rubbed with a sheet of clean paper. With glazed 
papers, however, the color must be bound with sufficient 
firmness so as not to rub off at all. Asa rule, a better 
quality of pulp-colors are employed in the manufacture 
of glazed papers than are in the printing of wall papers. 
Despite this, the same precautions governing the selec- 
tion of glue, as to the possibility of its affecting the 
colors, are to be observed. 

Since great clearness of the colored surface is a req- 
uisite, foreign glues are extensively used in the prepa- 
ration of glazed papers. Domestic acid-treated bone 
glues answer well and are frequently used. A water- 
proof coating is made by sizing the colors with a solution 
of shellac in wood-alcohol, crude acetone, or other 
solvent. Such surface, while water-proof, has not the 
clearness of the glue-sized surface. Some prepare a 
sizing medium by dissolving shellac in a strong, aqueous 
solution of borax. So long as the alkali is present, this 
cannot be water-proof and has not the clearness of 
good glue. A far better result is achieved by adding 
a proportion of potassium or ammonium bichromate to 
the glue solution, and exposing the coated papers to the 
influence of sunlight for a time, which renders the 
coating practically water-proof. This practice is at- 
tended with some risk, however, as every glue will not 
admit of treatment with a bichromate without suffering 
damage. Again, the colors themselves may not be 
permanent and the subsequent exposure to sunlight 
may cause them to fade. The cheaper varieties of 
surface-coated papers are prepared by coating them 
with a mixture of unprecipitated aniline color, sized 


SELECTION OF GLUES 125 


with casein. The use of casein in this connection is 
subject to the same limitations restricting it as a sizing 
~medium for wall-paper colors. 

Glues for Paper Boxes. — While many glue substitutes 
will answer for paper-box making, a cheap grade of 
glue is usually employed for the heavier work, and 
substitutes, such as Boston gum and Liquid Glue, for 
the lighter. The average paper-box maker seldom pays 
more than six cents per pound for glue, and at this 
price only a weak product may be purchased. This 
usually tests No. 2 and rarely exceeds 1? in strength, 
averaging 1f. Ground glues are always used, and these, 
as arule, very dirty. The standard grade of paper-box 
glue is the Swift Box. This is a medium brown, low- 
erade hide, averaging, in test, 1{. Very similar to this 
is the Nelson Morris No. 92. It must not be inferred 
that these are the only glues fit for paper-box making. 
They are merely cited as types. 

Almost any glue, weak or strong, that is properly 
made and sweet in odor will answer for this class of 
work. Apart from the considerations that an evil- 
smelling glue is to be avoided and that the boards used 
for colored boxes are, as a rule, so cheap and poorly 
colored that alkali or acid in excess is likely to spot 
them by discharging the color, no particular examination 
of the glue is required, save to determine whether or 
not the glue has adequate binding strength. Fully 
99 per cent of the trouble experienced by paper- 
- box makers is due to their own carelessness. Owing 
to a deplorable ignorance of the elemental properties 
of glue, it is constantly exposed to influences and con- 
ditions that cannot fail to impair its efficiency. The 


126 GLUES AND GELATINE 


melting-pot is exposed to the dust of the work-room 
and it is a common spectacle to see strips of board, 
sticks, and other refuse floating in the glue solution. 
Frequently muddy water is used to dissolve the glue. 
Intelligent application is essential to the successful 
working of glue for any purpose; and the fact that the 
paper-box manufacturer need not exercise the care in 
the selection of his glue that is demanded of the cabinet- 
maker, for example, does not warrant the lax methods 
of treating the glue in vogue at the majority of paper-box 
factories. 

Glues for Sizing Work. — Glue, as a general size, is 
employed largely by the house painter, either for the 
treatment of walls before painting or calsomining, or as 
the binding medium for the calsomine itself. Fairly 
cheap opaque glues are in great demand for this class 
of work, custom having decreed their use. These glues, 
known among the painting fraternity as “‘shell”’ glues, 
since, by a stretch of imagination, they may be said to 
resemble certain varieties of laminaria, are frequently 
made from pig stock, colored by the addition of very 
cheap material. Several grades of these are produced, 
the better testing as high as 14, while the poorer average 
1% to 13. That a pale-drying, uncolored glue answers 
the purpose as well, if not better, is indisputable, the 
inferior coloring material of these opaque glues often 
working to disadvantage. Of late years, prepared sizes 
have come into the market, consisting of mixtures of 
chalk and glue, clay and glue, whiting and glue, or — 
chalk, clay, whiting, and glue, sometimes with the 
addition of alum and soap. To prepare these for use, 
it is but necessary to add boiling water, in the required 


SELECTION OF GLUES 127 


proportion. The painter frequently desires to prepare 
these sizes for himself; and in this connection it must 
be pointed out that the selection of the glue for the 
size is largely dependent upon the nature of the materials 
to be sized. ‘To work properly in so strange a combina- 
tion as the above, it is essential that the glue be com- 
paratively pure, that is, containing no residual salts 
that are apt to react with the other ingredients of the 
formula. The selection of glues for these combinations 
presupposes their careful analysis. Since the flow of 
the glue is of importance, those with low viscosity in 
solution are to be given preference. At the same time, 
the glue must be fairly strong, in order that a minimum 
may suffice to bind the basic material of the size. 

Glue is frequently used as size in the manufacture of 
cotton batting, and it is customary to prepare a sizing 
solution such that, when applied to the cotton as.it 
passes into the drying machine, it is absolutely dry as 
the roll emerges from the machine. Comparatively few 
glues fulfil this requirement, despite the fact that the 
temperature of the drying room averages 200° I. The 
absorbent nature of the material sized is a source of 
unending trouble, too thin a solution of the glue being 
totally absorbed, with the result that the material 
emerges from the drying machine stiff as board. On 
the other hand, too heavy a solution of the size lies all 
at the surface, and does not dry with sufficient rapidity, 
despite the high temperature of the apparatus. To 
obviate this difficulty, it is customary to treat a very 
dilute solution of a fairly strong, clear glue with suffi- 
cient alum to thicken it. Herein lies a source of danger. 
Many glues are precipitated with alum, particularly if the 


128 GLUES AND GELATINE 


mixture of glue and alum remain warm in the kettle for 
some hours. This precipitate cannot again be brought 
into solution without the aid of acetic acid, and, while 
the supernatant fluid has weak sizing properties, it has 
_ absolutely no binding strength. Even though the glue 
is used up before the precipitate has a chance to form 
in the kettle, the extreme temperature of operation is 
apt to cause its separation before it dries, and the work 
becomes “‘streaky,’’ clear in spots and cloudy or dense 
in others. It is essential, therefore, if it is intended to 
thicken the glue with alum, that a preliminary test of 
the glue be made in the following way: One pound of 
the glue is dissolved in fifteen of water. To the hot 
solution is added about 10 per cent of alum, and the 
mixture is kept hot (without actual boiling) in the 
kettle over night. If any precipitate forms under these 
canditions, the glue is not fit to be used as a size in 
conjunction with alum. If none forms, the glue will 
work excellently under these conditions. 

This applies equally to the selection of glues for use 
in conjunction with alum and clay, alum and chalk, etc., 
to which soap is to be added to promote the slip of the 
size in application. The glue must be carefully tested 
in the presence of all the ingredients with which it is to 
be combined, individually as well as collectively, and 
any adverse result noted. The necessity of great care 
in the selection of glues for the manufacture of prepared 
calsomines, particularly the colored varieties, cannot be 
over-emphasized. 

Glue in Textile Manufacture. — In the manufacture 
of silk, wool, and other fabrics, glue plays an important 
part, either in conjunction with the dyeing processes or 


SELECTION OF GLUES 129 


as a finish. It finds considerable application to the 
manufacture of carpets, as well as special wall-coverings 
such as burlaps and tapestries. An exception to the 
rule that glue strength is of the first importance is to 
be noted in this connection. Since, in all these cases, 
the glue is used as a size in very dilute solution; and 
since it is brought in contact with sensitive colors, 
purity is by far a more important consideration than 
glue strength. Analysis of the glue destined for use in 
textile manufacture is essential in order that it may be 
established beyond peradventure of doubt that no dele- 
terious substance is present in the glue. For example, 
the presence of mineral acids and normal sulphites in 
a glue renders its use hazardous in the manufacture of 
woolens, since any notable proportion of these impuri- 
ties will reproduce light patches on dyed wool. Black 
woolens owe their color to logwood (hematoxylin plus 
hematin) mordanted by the oxidizing influence of a 
chromium salt. The logwood itself contains consider- 
able glucose, since this is employed to impart the 
necessary gravity to logwood extracts. It is difficult 
to combine glucose and solutions of glue. True, the 
glue solution is applied. ajter the logwood, with its 
constituent glucose, has dried; but it is not to be denied 
that the water of the glue-size has a solvent action on 
the glucose of the fiber, the glucose not being affected 
by the chromium salt. Hence, while the reaction be- 
tween the finish and the glucose of the fiber may be so 
subtle as not to be at once manifest, it will nevertheless 
proceed, and at a later day, long after the shipment of 
the goods, they may be ruined by spotting, ete. 

Silk finishing involves the use of more or less glue, 


130 GLUES AND GELATINE 


which is used in conjunction with dextrines and starches. 
That a preference should be expressed for very pale 
glues is but natural, in view of the fact that these dry 
with a very transparent coating, especially if applied 
dilute. At the same time, the use of very pale glues 
for finishing fabrics of any kind is attended by constant 
risk. The glue owes its very paleness to the fact that 
the liquors have been bleached with sulphurous acid, 
traces, and frequently more than traces of which remain 
in the glue, as well as salts of sulphurous acid. If these 
are a menace in the finishing of woolen fabrics, their 
action is all the more inimical to colored silks, in the 
dyeing of which far more delicate colors are used. A 
given shade on silk is produced by the combination of 
the minimum quantities of several different colors; and 
a glue used for finishing the silk, if it contain any of. 
the above impurities, is apt to discharge one or more 
of these, producing spots of the fastest color. Those 
familiar with the methods of the color-chemist in “dis- 
charge work” will have no difficulty in comprehend- 
ing this phenomenon. A pale blue silk, for example, 
may be produced by dyeing with a fast red in com- 
bination with a blue and a violet. Sulphurous acid will 
discharge the blue and the violet, revealing the red and 
causing the silk to be covered, apparently, with red spots. 

In many instances, silks, particularly black silks, are 
treated in the dye-house with glue in conjunction with 
the finishing emulsion of oil, acid, and soda. As a rule, 
a good quality of gelatine is used, the object being to 
correct any hairiness or fuzz of the silk produced by 
extreme temperatures in the dyeing. Dark imported 
glues answer as well as gelatine for the purpose and are 


SELECTION OF GLUES 131 


cheaper than gelatine. It is essential that the glue 
used in this way, or for finishing purposes, be a clarified 
one. ‘This assured, the color is of little importance, and 
it is always safer to use a rather dark glue than a light 
one, for the reasons above mentioned. A dilute solution 
of dark clarified glue dries to a remarkably light, trans- 
parent coating, and may be used for all save pure white 
silks. In addition to the regular test preliminary to 
purchase, the dyer should treat dilute solutions of the 
glue with all the colors he employs, permitting the 
mixtures to stand for a day or so that any untoward 
effects may be noted. ‘The finisher, not having definite 
data as to how each shade of silk has been produced, 
should subject the glue or gelatine to rigorous analysis 
and reject those exhibiting any sulphurous acid and 
more than traces of other mineral acids and salts. 

Glue for Matches. — The manufacture of matches is 
attended by considerable difficulty owing to the nature 
of the ingredients used. As to the identity of the 
individual ingredients, no secrecy exists; the art lies in 
their proper combination. The general formula for 
parlor matches is, glue, phosphorus, chlorate of potash, 
whiting, plaster of paris, and rosin. The glue serves to 
work these into a hot paste into which the ends of the 
match-sticks are dipped. 

It is readily seen that in so strange a combination of 
materials, every glue will not work. It is stated upon 
‘authority that, unless the customary proportions of the 
above ingredients are radically modified, none but im- 
ported glues will answer. The Irish Block C. and 
Block C. L., and the Walsall of English manufacture, 
are the standards of match glues. Domestic glues have 


132 GLUES AND GELATINE 


been used with success, but are troublesome in operation 
owing to the necessity of radically modifying the formula. 

Glues intended for use in match making should be sub- 
jected to careful analysis as well as tested for strength. | 
The function of the glue is not merely as a binding 
medium for the mineral ingredients. It is largely de- 
pended upon to prevent atmospheric oxidation of the 
phosphorus. Accordingly, it must be certified that 
the glue contains nothing likely to affect the phospho- 
rus, in addition to exhibiting a fairly water-proof coat- 
ing when dry. | 

Comparison of Straight and Mixed Ground Glues. — 
Although ground glues are invariably regarded with 
suspicion, much of the popular prejudice against their 
use is unwarranted. To suggest to some consumers 
that they are using a mixed glue is to seriously 
affront them. They at once conceive the idea that 
the glue is worthless, and that an attempt has been 
made to defraud them. While it is true that the dealer 
frequently mixes ground glues for the purpose of cheap- 
ening them, his motives in so doing are not always 
ulterior. Not only are ground glues most convenient 
in use, as they require but the minimum soaking or 
softening prior to melting, but they offer many advan- 
tages over flake, in that they may be made to conform 
more nearly to a given requirement. The dealer who 
is conscientious in the endeavor to sell glue on “test,” 
that is, to match the samples he submits with those. 
submitted to him by the prospective purchaser, has 
often to mix one or more glues in order to obtain a 
product conforming in strength and viscosity or other 
factors with those of the samples submitted to him. It 


SELECTION OF GLUES 133 


is at times possible to mix two or more grades of flake, 
with the same object in view. Hence the fact that the 
dealer submits a sample of mixed glue must not be 
always construed as an attempt at deception. 

Recapitulatory Remarks. — The uses of glue herein 
enumerated represent but a small proportion of its pos- 
sible. applications. They are cited as typical of the 
limits of application, by which is meant the least and 
the greatest that is expected of glue in actual work; 
and are chosen with a view of impressing upon the glue- 
user the fact that it is adverse to his interests to re- 
gard glue as so much cheese, to be bought, consumed, — 
and the stock replenished. It lies within the power 
of every consumer, small or large, to control the quality 
of a material for which he expends considerable in 
the course of a year. He has but to apply the rules 
of common sense to its selection and application in 
order to obviate 90 per cent of his ‘‘troubles.’’? Price 
has often to be relegated to second place in selecting 
glues, although it must always be considered. For 
many purposes, an impure glue is dear at any price. 
In other instances, to spend a few cents more per 
pound for glue is to effect an ultimate saving, para-- 
doxical as this may seem. He who wittingly fails to 
test glues prior to purchasing them and to insure that 
delivery is as per sample, on the ground that his time 
is too valuable to be devoted to such purpose, is as- 
suredly “‘penny wise and pound foolish.” He is a 

veritable mark for the unscrupulous salesman, who with 
~ glib argument, backed by a minimum of scientific fact, 
has no difficulty in persuading him that a glue that 
smells to Heaven has absolutely no odor. 


CHAPTER VII 


HOW GLUE SHOULD BE USED 


Ir would seem superfluous, after discussing in detail 
the nature and properties of glue, as well as emphasiz- 
ing the necessity of exercising the greatest care in 
its selection, to remark that its success in work will 
depend in a large measure upon intelligent prepara- 
tion and application. The normal and logical infer- 
ence is that this principle is self-evident to him who 
uses glue constantly; yet a careful study of the situa- 
tion reveals the fact that a number of consumers are 
totally indifferent to first principles in the preparation 
of glue for work, and that many, of seeming intelli- 
gence, entrust the melting and distribution to those 
who are ignorant of its very nature and seemingly re- 
gard it as less worthy of consideration than the 
sweepings from the factory floor. The average dealer 
in glue is the recipient of so many and varied com- 
plaints regarding the product he supplies, the majority 
without justification, that it becomes necessary, in fair- 
ness to him, to call attention to the fact that he is often 
as little to blame for the difficulties experienced with 
glue as he is for an unexpected fall of rain. The com- 
monest complaint in regard to glue is that it has a bad 
odor. Harrowing tales are heard by the dealer regard- 
ing the number of employees who were compelled to 

134 


HOW GLUE SHOULD BE USED 135 


suspend work owing to the unbearable stench arising 
from the glue which he has supplied. Quiet investiga- 
tion reveals the fact that the glue melting-pot has not 
_been cleaned, say for six months, and that there is 
nothing “‘off” in the odor of the glue. The author has 
seen this trouble arise only too frequently in wall-paper 
factories, where the carelessness of the men in respect to 
cleaning the melting-pots is proverbial. It is no exag- 
geration to state that 80 per cent of the difficulty expe- 
rienced with glue arises from carelessness or ignorance 
upon the part of the user, and that the remaining 20 per 
cent may be legitimately ascribed to the glue itself. 
The adage, ‘‘Cleanliness is next to godliness,” has a 
beautiful and significant application to the preparation 
and treatment of glue, not only in regard to melting it, 
but also to its distribution and other factors. Storage 
under adverse conditions will ruin glue long before it is 
used. In the matter of assimilating foreign odors, some 
glues are extremely sensitive and hence should not be 
stored with odoriferous chemicals, crude carbolic acid 
in particular. It is the practice of some consumers to 
store glue in damp and even wet places, and subse- 
quently complain that it contains undue moisture 
or is moldy. Others, again, unhead the barrels pre- 
maturely, exposing the contents to dust and dirt which, 
when the glue is brought into solution, accumulates at 
the bottom of the melting-pot, thus contaminating 
subsequent melts, or, if the solution is heavy, remains 
suspended therein and soils the work. While the con- 
sumer frequently has cause for legitimate complaint, it 
would redound to his credit if he would but apply the 
rules of common sense to the treatment of the glue. 


136 GLUES AND GELATINE 

Soaking or Softening Glue. — Considerable difficulty 
in manipulation arises from faulty practice in this re- 
spect. Precautions must be observed that will insure 
the uniform softening of the glue prior to melting. 
To this end, if in the form of flake, sheet, cake strip or 
ribbon, it should first be broken into small pieces with - 
a hammer. It is essential that all the glue be immersed 
in the water. If pieces are permitted to stick out be- 
yond the level of the water, the natural result is that 
such pieces will be only partially softened. When the 
melting proceeds, these will slip to the bottom of the 
kettle, and, in order to melt them, protracted heating 
at an excessive temperature is required. This means 
the radical impairment of the strength and adhesiveness 
of the glue. 

In the case of extremely thin-cut, high-testing glues 
it is often impossible to have all immersed uniformly, 
unless the melting-pot be capacious. Such glues are 
very light and hence the required weight frequently 
represents considerable bulk. The needful quantity of 
water may fail to cover one half or even two thirds 
of the glue in the pot, with the result that the un- 
covered portion is not softened. This difficulty may 
be avoided at the expense of minimum time and 
trouble. Thin-cut, high-test glues absorb water rapidly, 
and hence if the requisite quantity of water is first 
placed in the melting kettle and the glue added little 
by little, each portion will soften rapidly and may then 
be shoved down toward the bottom of the kettle to 
make room for the addition of the remaining portions. . 
In this way the glue will be uniformly softened. 

Even though the pieces are well covered with water, 


HOW GLUE SHOULD BE USED 137 


it is necessary that they be stirred in the latter, when 
it is added, to insure uniform wetting. If this precau- 
tion is neglected, pieces will adhere to each other and 
the center of such masses will be quite hard even 
though the exterior is well soaked. These partially 
soaked masses require protracted heating at the expense 
of the whole solution, in order that they shall melt. 

The usual practice in wetting ground glues is to 
place the glue in the kettle and then pour on the water, 
stirring the while. No matter how carefully this is con- 
ducted, particles of the glue will rise to the surface of 
the water and float there, and, coming in contact with 
the sides of the kettle, stick there, giving up any ab- 
sorbed water with great rapidity and so do not dissolve. 
This very objectionable feature may be avoided as fol- 
lows: Put the glue in the kettle and add about half of 
the requisite quantity of water, stirring the glue with a 
stick, beginning the stirring before the water is added 
and continuing until the glue has absorbed as much 
water as it will. Now add the balance of water, stir- 
ring the while. Through the absorption of water from 
the first portion added, the glue becomes much heavier 
and when the balance is added there is no _ possibility 
of particles floating at the surface. 

Melting the Glue. — 'I'wo forms of i eich or 
kettle are commonly known, the one jacketed, and the 
other in which steam is introduced direct or ‘‘live.”’ 
The former is the better. Direct steam is injurious to 
solutions of glue, the drastic action of the steam rapidly 
weakening them. If a solution of A Extra be boiled 
continuously with direct steam for a period of twenty- 
four hours, the gelatinizing power of the glue will be 


138 GLUES AND GELATINE 


destroyed. The gelatinizing power of weaker glues is 
destroyed in correspondingly shorter time. If a solu- 
tion of glue is boiled with direct steam for one hour, it 
will lose a grade in strength, and a half-grade if kept at 
200° for one hour in a jacketed kettle. It is to be 
borne in mind throughout the melting of the glue, that 
no more heat is to be applied than is absolutely neces- 
sary. If direct steam is employed, it is folly to boil the 
water until all is dissolved; besides, it is not necessary 
to do so. Let the steam pass through the water until 
the temperature is 180° F. If no thermometer is at 
hand to measure the degree of heat, this may be approx- 
imately gaged by the cessation of the characteristic 
rattling noise produced by steam when passed, under 
pressure, into cold water, and is supplanted by a sub- 
dued rumbling. When this degree of heat is reached, 
cut off all steam and stir the contents of the kettle 
until all the glue is uniformly dissolved. If the glue 
has been properly softened, it will dissolve at a low 
temperature. 

Under no circumstances should hot or even warm 
water be poured upon dry glue. The heat, so far from 
facilitating the softening, actually retards it, if not 
preventing it altogether. We have a parallel phenom- 
enon in the treatment of iron with nitric acid, the 
action of which is first violent and finally ceases alto- 
gether, owing to the fact that a slight film of oxide of 
iron is deposited upon the surface of the metal under- 
going solution. This is repeatedly dissolved and re- 
deposited by the acid. In order to promote the 
solution of the metal, it becomes necessary to pour off 
the acid and wash the metal well with pure water. 


HOW GLUE SHOULD BE USED 139 


When the acid is returned, it again attacks the iron 
violently. The action of the hot water on the glue is 
to dissolve a little, which, when once in solution, seems 
to retard, if not altogether prevent, the further absorp- 
tion of water by the glue. This may easily be verified 
by preparing a 2 per cent solution of glue and placing 
in this a piece of glue to be softened. It will be found 
that a much greater time is required than if the piece 
had been immersed in pure water. 

Where steam is not available for melting the glue, 
and the direct heat of gas or oil has to be used, the 
melting-pot must be jacketed, as otherwise the solution 
will burn and char. The outer jacket is to be filled 
with water, which, when brought to the boil, will impart 
sufficient heat to the water of the inner vessel to melt 
the glue. Once the water in the outer jacket is at the 
boil, the heat should be withdrawn. 

The facility with which glue melts will depend upon 
its proper softening. If this detail is attended to, there 
should be no difficulty in obtaining a uniform melt: at 
the minimum temperature. In reply to the oft-empha- 
sized dictum that the glue solution should not be kept 
continuously at a high temperature lest the adhesiveness 
and strength of the glue be impaired, it is justly con- 
tended that, since the solution must be hot in order to 
be effective, especially in joining wood, it is imperative 
that the melt must be kept at a certain degree of heat 
in order that time shall not be lost by having to stop 
work to reheat the cooled or jelled solution. Since this 
continuous heat is maintained to save time in work, it 
is inevitable that a skin form on the melted glue, which, 
brushed aside, clings to the pot and dries there, usually 


140 GLUES AND GELATINE 


beyond the level of the water added for the next melt. 
How continued high temperature, and consequent for- 
mation of skin may be avoided, will be seen further on. 

Cleaning the Melting-Pot. — Not only is it essential 
that the melting-pot be kept scrupulously clean in order 
that there shall be no gradual contamination of the 
glue, but much waste of material is avoided through 
this observance. Dirt enters the melting-pot through 
the glue itself, the introduction of dirty brushes, or the 
exposure of the pot to dust, etc. If glue is melted in 
a dirty pot, the skin forming on the surface of the melt 
eradually accumulates at the sides of the kettle and 
slowly decomposes. This may or may not fall into 
subsequent melts, thus contaminating them. The only 
way to make sure that it will not do so is to clean the 
pot. 

Much unnecessary waste of glue may be avoided 
through observance of the following procedure. The 
contents of the melting-pot exhausted, scraps of dried 
glue, as well as scraps of partially dried jelly adhering 
to the sides, should be detached mechanically, as thor- 
oughly as possible, and examined. If clean, they may 
be replaced at the bottom of the kettle; if dirty, they 
are to be set aside temporarily. In the first instance, 
they are covered with the minimum of water necessary 
to soften them and the sides of the kettle swabbed with 
a little water in order to soften any glue that has dried 
and not been detached mechanically. The pot is then 
gently heated in order to bring the scraps into solution, 
this solution used in work, and the pot thoroughly 
washed out with hot water and cooled before soaking a 
fresh portion of glue. If the scraps have proved dirty, 


HOW GLUE SHOULD BE USED 141 


but not sour, they may be re-melted in a separate kettle 
and the solution kept warm enough to permit the dirt 
to settle, when the supernatant glue may be used 
without risk. If sour, they must be thrown away. 
If the glue pot is properly cleaned, there is no danger 
of souring, and thus all the glue may be used without 
waste. It may be contended that much labor may be 
saved by adding sufficient water for the next melt, and 
through this means soften all glue adhering to the 
kettle in conjunction with that added fresh. It will 
be found, however, that the freshly added glue will 
absorb the bulk, if not all, of the water, leaving adhering 
scraps practically unsoftened, which in this way con- 
tinue to accumulate, interfering with the proper working 
of the glue. 

Distributing the Glue. — The most economical method 
of handling glue is that adopted at a number of pro- 
gressive factories where large quantities are consumed. 
The glue is first softened and melted in a large central 
kettle, the solution being made very concentrate so that 
a stiff jelly results. This jelly is then divided into 
small portions and distributed among the workmen, 
whose benches are equipped with small melting-pots. 
The workers have then merely to re-melt the jelly with 
the addition of water, this re-melting requiring but a 
minimum temperature. The advantages of such system 
of distribution are, first, that but a minimum of glue is 
apt to be damaged in the melting, as this is entrusted 
to some one who understands what he is about; second, 
that there is comparatively little or no waste of the 
clue, the portions of jelly distributed being carefully 
checked, and it is thus seen that no workman uses more 


142 GLUES AND GELATINE 


glue than another for a given purpose. Thirdly, the 
danger of contamination by dirt or partially foul scrap 
from previous melts is reduced to a minimum, as there 
is but one large kettle to clean, and the cleaning of the 
smaller bench-kettles is readily effected. The chief dis- 
advantage of the system arises from the fact that glue, 
in the form of a jelly or in solution, is far more prone 
to decomposition than when dry. Unless the system 
is so regulated that the minimum amount of jelly is 
prepared and distributed so that it will be rapidly 
consumed, loss is apt to be occasioned by the souring 
of the jelly, especially in warm weather. This difficulty © 
may be obviated through the judicious use of any 
preservative save formaldehyde. The addition of a 
small amount of pure carbolic acid, for example, will 
insure against decomposition of the jelly for a day or 
so, and will not impart sufficient disagreeable odor to 
affect the work. If the use of preservatives is objected 
to, the keeping quality of the glue may be enhanced by 
pouring the solution of glue into small tin boxes to jell. 
These should be provided with a tightly fitting cover 
and should always be kept closed save when portions 
of the jelly are to be withdrawn. Definite quantities 
of glue jelly may in this way be distributed, as boxes 
holding one pound, or any other desired quantity, may 
be selected for the purpose. The atmosphere excluded 
as far as possible, the glue will keep well. In Jelling 
the glue, the cover of the boxes should be left off until 
gelatinization sets in. 

Davidowsky points out that, while glue is fresh made, 
every addition of water will, up to a certain point, 
increase the adhesiveness and elasticity of the glue. 


HOW GLUE SHOULD BE USED 143 


This is true only of glue in the form of jelly, and the 
fact is largely commendatory of the system of at once 
converting the glue into a stiff jelly and then distributing 
this for use. This practice certainly increases the water- 
taking quality of the glue. Even as glue stock yields 
more and more glue as water is added up to a certain 
limit, so glue itself would seem to yield greater strength 
and adhesiveness to large quantities of water than to 
small. From this it would seem that glue, as prepared 
from the stock, is never chemically complete, but requires 
the addition of water and subsequent treatment with 
heat in order that the hydrolitic action, to which it 
owes its very nature, shall be completed. This peculiar 
behavior of glue jelly would further indicate that 
gelatinization is attended by partial reversion to the 
form of the glue-yielding elements of the stock, and 
that when the jelly is treated with additional water, 
an increase of actual glue is effected. 


CHAPTER VIII 


COMMERCIAL AND LEGAL ASPECTS 


Trade Conditions Affecting the Price of Glue. — Close 
study of the glue industry reveals conditions extant in 
few, if any, other lines of business. The laws of supply 
and demand, universally recognized as the basic in- 
fluences affecting the price of any commodity, are here 
factors of but secondary importance; and, while it is 
true that the price of glue is subject to the same natural 
trade influences affecting the majority of manufactured 
products, such as cost of production, which, in turn, is 
subject to scarcity of stock or lack of economical pro- 
cesses of production, and scarcity of glue itself, the 
glue market is in the main controlled by purely artificial 
considerations. Few, if any, products require the selling 
argument necessary to dispose of glue, an argument 
that draws freely upon the realm of fiction for its 
presentation. 

It is an established and accepted principle, among 
manufacturers and dealers, that the market price of 
glue is any price that can be obtained. Under existing 
business conditions, this applies, to a limited extent, to 
any manufactured product. The seller of any com- 
modity will take advantage of the credulity of the 
purchaser in the endeavor to realize an increased profit; 
but the seller of glue has far greater latitude in this ~ 

144 


COMMERCIAL AND LEGAL ASPECTS 145 


respect, inasmuch as the commodity in which he deals 
is but little understood and is not subject to sale under 
specification. 

A consumer who is in need of lubricating oils, paint, 
or other product, the sale of which is subject to specifica- 
tion, even though he know absolutely nothing about 
the material he contemplates purchasing, has always a 
limited degree of protection, in that he may consult 
some authoritative list of prices current, and thereby 
inform himself, within certain limits, of what he may 
be called upon to pay. The uninitiated consumer of 
glue enjoys no such advantage. As a practical demon- 
stration of this lack of data for guidance, the ‘absence 
as it were, of any suggestion of a definite market value 
of glue, we may assume that an individual, A, con- 
templates the purchase of a lubricating oil. He refers, 
let us say, to the following list of wholesale prices 
current: 

MINERAL OILS. 
Black, reduced, 29 gravity, 25@830 cold test, 103 @11 cents per gal. 


29 : 15 ae es 114 @124 é Cees 

ean POrO Bis oe wl fh (GA yea ee ee 

SCI Fy SS Sal Pa iar eh 104 @114 “ Oo Pak 

MeV PMGeGe HONG, TIGCTCU.. cw. ee ee eae TSA 19S Cee fie 
Gu) “CRISS Raat ei aver De reerer aoe 16¢ GATS 

OE TS a ae ee 224. @294 ates 
BoindiesNo: dD altered.. 2... . 6 ee eee 1Sp lie Covet 
a) UN Bi ae a ee eae 12°13 ee a 

Rm ik ee et, 11 @12.“« « «& 

PIER erates inci < S's e's ci Phe aia a ee 10 @1l: “ Ge RS 

RR ees Sc. cries aban) bs OL 0 Gas sae 


etc., etc., etc. 


This is an approximately correct quotation of the 
market price of oils at a given date, and were A to 


146 GLUES AND GELATINE 


apply for the individual quotations of a dozen dealers 
in lubricating oils, he would find that the prices named 
by them conformed in the main with those quoted 
above. 

Again, let us assume that A is a novice in the purchase 
of glue. He is about to embark in a line of business 
. entailing the purchase of considerable glue at the outset. 
Lacking any definite information as to the kind of glue 
he requires for his particular work, he at once consults 
a list of wholesale prices current published in some 
reputable trade journal. This is what he gleans: 


i A) GLUES 

SAP bo 8s OS ass He ree 18 @ 24 cents. per lb. 
Médium whites... sce. 9 a 2 ee 14:6 12038 Lape. 
Us bametese OR cue koran ee cake He Tene 11 18 eee 
Low grade). 5) 2. c.ct0 eae ere ee eee 0:@ 12.7 
Foot, stock, white (2.05 9220s ck eee 11.0 14:4") ae 
+ $65) DPOWD 7 oo28 ctu cece 8. 14 ee 
Common Jboné oir sn aie oe 7[@ 6-5 ae 
Trish. 2 AE Sey Cue ke eee 13@ 16..7 ten} 
French: sien oes ee oe eee 10 @ 40-224 La: 
Germian i Hid64: 29%). tc Saba eis eee 12:@18 ee 
yy COMMON Mead oc Us eee 10@ 11 ee 
Fish glue, liquid, in barrels, 50 gals. each ...... 50 @ 1.20 per gal. 


Now, were A a consumer of oils, even though he had 
never before purchased any, he could readily learn that 
Spindle oil, for example, will not answer for the lubri- 
cation of engine cylinders. He has only to know the 
particular grade of oil required for his work, Spindle 
No. 1, for example, when he may form some definite 
idea as to the cost, which will be 12 or 13 cents per 
gallon on this day. He may inform himself of this, 
for the reason that oils are sold under specification, and 


COMMERCIAL AND LEGAL ASPECTS 147 


hence the prices quoted are approximately correct. Not 
so with glue. Were our friend embarking in the manu- 
facture of paper boxes, for instance, he might use with 
success any of the glues quoted in the above list and 
thus pay anywhere from 7 to 40 cents per pound. The 
chances are that he does not know a bone glue from a 
hide and, upon consulting the above list, might at once 
conceive the notion that French glue is the best on 
earth, since it costs more than any other. Two courses 
of action are open to him. He may either hazard the 
purchase of a medium-priced glue and eventually, by 
running the gamut of all the glues offered him, learn 
that a sweet 7-cent glue will answer as well as one at 
25 cents for paper-box work, or he may apply to the 
nearest dealer for information on the subject. Woe 
betide him if he does! In event of the prior contin- 
gency, his experience will be gained only at the outlay 
of considerable money. In the event of the latter, the 
information he would glean in some cases would, if 
published, contribute materially to the gaiety of nations. 
The dealer, proceeding upon the established principle 
that the market price of glue is any price that can be 
obtained, will at once take advantage of the applicant’s 
credulity to impress upon him the necessity of using a 
particular grade of glue representing the maximum 
margin of profit to the dealer, although, possibly, the 
minimum of efficiency to the consumer. This the con- 
sumer will use until another enterprising dealer offers 
him something cheaper. 

That the above list of quotations is of but little value 
in assisting the uninitiated to form some estimate of 
the price of glue will be seen from the following con- 


148 GLUES AND GELATINE 


siderations. In the first place, Extra White glues are 
quoted at 18 @ 24 cents per pound. These may range 
in strength from No. 2 to A Extra and it vs this strength 
that will determine their cost. Thus, a good opaque 
A Extra hide glue may cost 17 cents per pound, whereas 
an “ Extra White” glue for painters’ use, which is made 
largely from pig stock, may cost not more than 10 cents 
in the same market. Similarly, cabinet glues are of 
different strengths, and it is this that will determine 
their cost. The only glues that may be said to have a 
definite market value, that is, having prices that 
fluctuate in accordance to universally recognized trade 
conditions, are imported glues, such as Irish, French, 
and German, which, in the above list, are quoted with 
some degree of correctness. There is a fixed duty on 
these glues, and hence the manufacturer’s price, or first 
cost, is always such as will permit his product, with 
the addition of the duty, to meet the domestic in com- 
petition. 

Just as the term “cylinder oil’? conveys no informa- 
tion beyond the fact that it is to be used in the lubri- 
cation of engine cylinders, and the price will depend 
upon color, consistency (gravity), flash point, and cold 
test, so the terminology ‘‘cabinet glue” is indefinite 
unless we specify the strength. Through experience, 
buyers of glue in large quantities, for any purpose 
whatsoever, may always inform themselves, to a limited 
extent, as to what they will be called upon to pay, 
inasmuch as they are aware that the price will, in the 
main, be controlled by the strength of the product. 
If any information is to be gleaned from a list of whole- 
sale prices current, this must be based upon the esti- 


COMMERCIAL AND LEGAL ASPECTS 149 


_ mates of a number of leading manufacturers and dealers, 
and must be tabulated in the following way: 


GLUES 
AT soi es ol Lidih cee'd i vaso ao y ee 18 @ 20f. 
Prieta. Gane (WHILE). ...... 5.2.5.0 cae ae 18 @ 22¢ 
TE cs hea ce eee aves cae 18 @ 21”. 
MRTG ery is, a ae wey eM els Bw oe 15 @ 19%. 
diextra,colored and opaque ................ 17 @ 202 
ESS 14 @ 18%. 
Brrr eolored 2nG Opaque ..,....%,...22..+.- 15 @ 19” 
Ce ee Dek a ee bes 13 @ 16¢. 
Pececorored and opaque ..........6 0.0. ..s ee 14 @ 17% 
Bemereises cromels CO lt. ee ule ee ee 10 @ 18¢. 
Bone glues, common, according to test ....... 6@ 9Y9¢. 
Bone glues, acid-treated, according to test .... 8@ 12%. 


The inexperienced buyer has now only to know that 
glues ranging in strength from 13 to A Extra are cabinet- 
glues, the particular grade being determined by the 
nature of the work itself, or that common bone glues 
are useful for box work, all other factors being equal. 
Such a list will then assist him in forming some estimate 
as to the cost of the glue on a given day. As a matter 
of fact, the glues are so classified by the majority of 
manufacturers and dealers, who are nevertheless reluc- 
tant to apprise the consuming public of this, lest they 
no longer have an opportunity of realizing increased 
profits through the inexperience and credulity of the 
consumer. 3 

Cost of Glue as Affected by Scarcity. —The bogy of 
a high market, due to scarcity of glue in general and the 
consumer’s favorite brand in particular, is one of the 
chief selling arguments for glue. The safest remark for 
a salesman to make, when approached as to the cost 


150 GLUES AND GELATINE 


of his wares, is, ‘‘that the price of glue has advanced, 
generally.”” -As a rule, the consumer has absolutely no © 
way of informing himself to the contrary and thus the 
way to an increased margin of profit for the dealer is 
nicely paved. 

At intervals there is a genuine scarcity, not of all 
glues; but of some particular grades. Nor is this always 
owing to natural causes, such as decreased production 
because of temporary scarcity of stock, but simply to — 
the fact that a number of manufacturers may agree, 
among themselves, to hold back their cheap grades for 
the time being, in order that there shall be an increased 
demand.for them and in this way a better price realized. 
Again, some astute jobber may gradually accumulate 
a vast quantity of low-grade glue, thus creating a 
genuine shortage on the part of the manufacturers, 
preventing them from meeting their own goods in com- 
petition, when the jobber is able to realize almost any 
price he may ask so long as his stock holds out, or un- 
til manufacturers themselves have once more reached 
their average production of the glues in question. 

It may safely be asserted that there can be no natural 
scarcity of glue so long as the packing and leather in- 
dustries are in existence; and these will continue as long 
as man evinces the desire to eat flesh and wear shoes. 
Given a number of oxen, sheep, and pigs to be slaugh- 
tered daily, there will always be the same number of 
hides for tanning and hence so much hide stock for 
glue. So many bones will be obtained from the car- 
casses, which will produce a given number of knife- 
handles, buttons, and a definite quantity of bone stock 
for glue making, with its attendant refuse for fertilizer 


COMMERCIAL AND LEGAL ASPECTS 151 


compost. It is to be remarked: that scarcity is usually 
confined to the low and medium grade bone glues as 
well as the inferior mixed bone and hide glues produced 
by our large packing houses. Seldom is the price of 
high-grade hide glues, produced at independent facto- 
ries, affected by scarcity; and when this does occur it is 
legitimately due to lack of stock. These factories are 
dependent for stock upon the tanner, and, as the latter 
does not produce a definite quantity of waste or glue 
stock, the glue-maker cannot rely upon any one tannery 
for a uniform supply. Again, the tanner may so modify 
his processes, when dealing with some particular ship- 
ment of hides, that the stock coming to the glue boiler 
may demand totally different treatment than he is 
accustomed to give; with the result that he produces, 
for the nonce, a grade of glue different from those hith- 
erto produced by him. In this way a temporary 
shortage of some one particular grade of hide glue is 
created; but this does not mean the scarcity of hide 
glues in general. ) 

There is a greater demand, on the whole, for low-grade 
glues than for high grades, as the former are applicable 
to the majority of usages and are cheaper than the latter. 
Hence the tendency to create a shortage of these grades 
in either of the above-mentioned ways, in order that 
they may command an advanced price. Were the con- 
ditions reversed, 7.e., were the demand for hide glues 
greater than that for bone, endeavor would be directed 
to the cornering of these. 

Position of the Jobber in the Trade. — The jobber of 
glues occupies a position in relation to the manufacturer 
and the consumer that is at once advantageous and 


152 GLUES AND GELATINE 


unique. His are not merely the functions theoretically 
accorded the ‘‘middleman.” Eliminate him, and the 
entire scheme of things, as regards the conduct of the 
glue industry, would require readjustment. We refer, 
not to the small jobber whose stock, at any given time, 
seldom exceeds twenty or twenty-five barrels of glue, 
but to him who, through resource of capital, enabling 
him to buy virtually for cash and anywhere he pleases, 
carries a stock of a thousand barrels of glue at any 
given time. Many consumers labor under the delusion 
that they lose money by dealing with the jobber, flat- 
tering themselves that they can buy as cheaply as he. 
Indeed, this is one of the strongest arguments advanced | 
by the manufacturer’s representative in approaching 
the consumer direct. To realize how little truth there 
in is this contention, the reader has but to bear in mind 
that, in the purchase of any commodity, he who pur- 
chases in large quantities obtains a better price than he 
who purchases but small packages, and that to every 
barrel of glue purchased by the consumer, the jobber 
requisitions twenty. Which, under these conditions, is 
enabled to buy cheaper? ‘The question is superfluous. 
It might seem, at first inspection, that the position of 
the jobber is a perilous one; that, were manufacturers 
resolved to shut down on him, he would be compelled 
to suspend business. This is true of the small jobber, 
who, through lack of capital, is unable to buy in the 
open market, as it were, and must confine his dealings 
to some one manufacturer who is willing to extend to 
him liberal terms of credit. He can continue in business | 
only so long as the manufacturer who supplies him 
agrees not to approach his customers. On the other 
id 


COMMERCIAL AND LEGAL ASPECTS 153 


hand, the large jobber enjoys all the advantages and 
suffers none of the responsibilities of the manufacturer 
himself. The grades he carries are more varied than 
those produced at one factory, since he buys from a 
number. His purchases are uniform. He is very care- 
ful to see to that. Again, his resources are such as to 
enable him to control the output of a number of minor 
factories, and in this way he becomes virtually a manu- 
facturer himself without having to bother about secur- 
ing stock. He merely agrees to take the entire output 
at such and such a price. That the jobber is recog- 
nized as an indispensable factor in the glue situation 
_by the manufacturer, despite any arguments he him- 
self may advance to the contrary, is evidenced by 
the fact that the latter is ever ready to supply the 
former with vast quantities of glue at a favorable price. 
Indeed, to refuse to do so would be to antagonize his 
best interests. As an illustration, we may cite the sale 
of a carload of glue (sixty barrels) to sixty separate 
consumers, scattered over a large territory, on the one 
hand, and, on the other, the sale of a carload, as such, 
to the jobber. In the first instance, although a far 
higher price is realized in the sale of the individual 
barrels, the selling-cost is proportionately high. In 
the second, a relatively smaller selling-cost is entailed, 
with the paradoxical result that by accepting a lower 
price the shipper realizes a larger profit. Again, were 
it not for the jobber who is ever ready to avail himself 
of favorable offerings of glue, particularly cheap grades, 
the manufacturer’s stock would accumulate to such an 
extent that it might ultimately have to be disposed of 
at a loss. 


154 GLUES AND GELATINE 


In view of all this, it is seen that the jobber is in 
relatively better position to supply the trade than any 
one manufacturer. He handles a far greater variety of 
glue and, by effecting combinations, comes nearer to 
selling glue under specification than the manufacturer. 
He can keep his trade only by selling glue “to match,” 
and when a prospective purchaser submits a sample of 
the glue he is using, this is carefully tested and a counter- 
sample submitted practically duplicating the original in 
color, cut, strength and other test factors. The accom- 
plishment of this presupposes the carrying of a large 
and varied stock of glue, as it is often necessary to 
combine two or more glues to match the test factors 
of another. In this way, the jobber has the advantage 
over the manufacturer who produces but a limited 
number of grades and these regularly. Again, the 
jobber frequently recognizes in the submitted sample 
a well-known make of glue and may be carrying this 
in stock. He is thus enabled to offer the manufacturer’s 
own goods in competition with him. Despite the fre- 
quent occurrence of this, but few manuacturers with-— 
- hold their supply from the jobber. 

The Consumer’s Redress in the Law. —If another 
argument is needed to impress upon the consumer the 
necessity of constantly testing his glues, it is embodied 
in the fact that, unless he does so, he will never be able 
to recover for losses caused by defective glue. The 
legal maxim, “‘Let the buyer beware!” applies with 
great force to barter in this commodity. An example 
of the general application of this principle is as follows: 
If A sell B a horse, and the said horse lacks a tail at the 
time of purchase, B cannot recover the purchase price, 


COMMERCIAL AND LEGAL ASPECTS 155 


nor could he bring any action for damages on these 
erounds. It is B’s business to note the absence of tail 
before handing over the money to A. On the other 
hand, if said horse develop some disease within a few 
days after purchase, an action against A for the recovery 
of the money paid will lie, unless it can be proved that 
said disease was contracted after the horse had passed 
into B’s possession. ‘The law thus creates the distinction 
between visible and latent defects. 

As applied to glue, this principle operates in the 
following way: A consumer has received regular ship- 
ments of glue of a certain kind; for example, a straight 
hide glue. In color this was, we shall say, dark brown, 
and the glue was in the form of oblong sheets. A 
shipment arrives consisting of flake glue of two colors, 
one light yellow and the other brown. The consumer 
uses this in the work, which is thereby ruined. It is 
evident that the glue is totally different in character 
from previous deliveries. Despite this he cannot legally 
refuse to pay the bill, nor is entitled to damages for the 
ruined work, inasmuch as a visible defect existed in 
the glue. This would apply to taste and odor as well. 
It is for the consumer to examine the glue on arrival, 
and, noting the defect, to return it to the shipper or 
hold it at the latter’s disposal. If the latter refuse to 
take it, the former is not liable for the bill. He cannot, 
however, use the glue and expect immunity from 
payment. 

Although it is possible to recover for latent defects 
in glue, it is extremely difficult to prove these. What 
more difficult to prove, for instance, than that certain 
chemical conditions existed in the glue which, in com- 


156 GLUES AND GELATINE 


bination with outside influences, produced a disastrous 
result? The testimony of the analyst, however compe- 
tent, too often demonstrates that the defect was visible 
and not latent, in the construction of the law. 

It would thus seem that the consumer has but little 
or no redress in the law and must seek protection 
through other means. He can find it only in the 
careful testing and comparison of samples and deliveries 
and the prompt rejection of those that are not as 
represented. 


CHAPTER. IX 


MANUFACTURING RECEIPTS 


THE following working formule are all practical, 
having been tested by the author. A number represent 
standard formule which have been hitherto published 
in a number of works on glue, having been known for 
years to investigators. Others, again, are the result of 
the author’s personal experience. Carefully carried out, 
they will all yield satisfactory results. 

Water-proof Glues. 

A. Glues rendered water-proof by mixture with other 
substances. 

1. Glues may be rendered practically water-proof by 
the addition of a small quantity (1 per cent) of ammo- 
nium or potassium bichromate to their solutions. The 
glue becomes water-proof only upon exposure to the 
_ influence of the sun’s rays. 

2. The addition of a limited quantity of formaldehyde 
to the aqueous solution of glue will aid it in resisting 
the action of water after it has dried for a time. 

3. Ten parts of glue are soaked in an equal volume 
of water and the glue removed before it has lost its 
primitive form. The swollen glue is’ then dissolved in 
about 10 parts of linseed oil, with the aid of heat, until 
a jelly is formed. This mixture is an effective cement 
for joining a number of materials and is practically 
water-proof, 

157 


158 GLUES AND GELATINE 


4. Twelve parts of glue are dissolved in 15 of water. 
Two parts of bleached rosin are added and the heating 
continued until the rosin and glue are uniformly incor- 
porated. Four parts of turpentine are now cautiously 
added and the whole stirred until uniform. 

B. Water-proof Substitutes for Glue. 

1. Dammar and other cheap varnishes are sufficiently 
sticky to fulfil the adhesive requirement of glue, and 
possess the advantage over the former in that they are 
absolutely water-proof. These cannot be used as 
water-proof coatings. 

2. Shellac may be dissolved in wood alcohol to the 
consistency of a heavy solution of glue and may be 
used as a water-proof glue in the lighter work to which 
glue is applicable. 

3. Marine glues are water-proof cements containing 
no glue whatsoever. They are admirably adapted to 
the calking of vessels, whence, in all probability, their 
name. Jeffrey’s marine glue is prepared by incorporating 
shellac with a solution of 1 part of india-rubber in 
benzine. Others are combinations of solutions of rubber 
in refined petroleum (1 part rubber, 12 parts solvent) 
with 20 parts of asphaltum. The asphaltum is melted 
separately in an iron boiler and the rubber solution 
added in a thin stream, the whole stirred until uni- 
form. 

Mending Cements. — These comprise numberless prep- 
arations of greater or less value. Some few give satis- 
factory results and are here described. 

A. Cements for Iron and Other Metals. 

1. Marine glue, above described, may be used to 
advantage in cementing metal to metal, 


MANUFACTURING RECEIPTS 159 


2. A cement for pipe-joints is prepared by mixing 
red lead with linseed oil to a thick paste. 

3. Diamond cement for metal. Into 40 parts of 
linseed oil there are slowly stirred the following, in 
order named: Litharge, 30 parts; slaked lime, 10 parts; 
whiting, 20 parts; and graphite, 100 parts. The cement 
is to be applied hot to the slightly roughened surface 
of the metal. 

4, An oil cement for steam-pipes, which is free from 
lead, is prepared by mixing intimately 1 part of graphite, 
3 of heavy spar, 1 of slaked lime, and 1 of linseed oil. 
The mineral ingredients are first to be mixed well and 
the mixture incorporated with the linseed oil. 

5. Casein, 8 parts; slaked lime, 10 parts; quartz sand, 
10 parts. In place of the sand, finely divided silex 
(silica) such as is employed to ‘‘fill” scouring soaps, 
may be employed to advantage. 

6. For uniting metals, a strong cement is made by 
the addition of good quality whiting (Extra Gilder’s 
will answer) into a solution of silicate of soda (water 
glass) of 40°. Be. Sufficient whiting is added to form 
a plastic mass. This cement has the advantage in that 
it may be colored by the addition of such substances 
as antimony sulphide for black, cupric carbonate for 
light green, chromium oxide for dark green, etc. 

B. Cements for Porcelain and Crockery. 

1. White pitch, 9 parts; sulphur, 14 parts; bleached 
shellac, 2 parts; gum mastic, 4 parts; gum elemi, 4 
parts; finely powdered and sifted glass, 14 parts. All 
ingredients, excepting, of course, the glass, are to be 
melted together and the glass stirred into the melted 
mass, 


160 GLUES AND GELATINE 


2. Gutta-percha, 1 part, and shellac, 1 part, are 
cautiously melted together by the aid of indirect heat, 
preferably by placing the vessel containing them over 
the water-bath. The melted ingredients should be well 
mixed and applied hot, having previously warmed the 
edges of the pieces to be cemented. 

3. Casein, 10 parts, is dissolved in silicate of soda, 
100 parts, by constant shaking of the mixture. If 
applied rapidly, this is a most effective cement for 
mending crockery and glassware that is to be heated. 

C. Cements for Glass. , 

1. For mending broken glassware, provided this does 
not have to be heated, there is no better cement than 
water-glass itself. This must be carefully applied, 
special care being taken not to smear the surface of 
the glass as, once dried, the cement will never come off. 
It is best used in fairly heavy solution and applied by 
means of a fine camel’s-hair brush which should at once 
be cleaned by dipping it in boiling water. The fractured 
edges of glass should be just slightly roughened with a 
new file (triangular or flat), the cement applied quickly, 
and the cemented pieces firmly pressed together. Should 
this procedure squeeze any cement from the joint over 
the surface of the glass, it should at once be wiped 
away with a cloth that is just damp, not wet. For 
mending cracked bottles or flasks, these should first be 
warmed so as to expel the air, immediately corked, 
and the cement at once applied to the cracks. As the 
bottles cool, the air will be drawn in through the crack, 
and in this way the cement will be drawn from the 
surface into the crack itself, where it will harden. 

2. For glass upon glass, dissolve, with the aid of 


MANUFACTURING RECEIPTS 161 


jacketed heat, 10 parts of shellac in 2 of turpentine, 
and to this add 10 parts of finely powdered pumice 
stone, the cement to be used hot. 

3. For glass upon metal, melt together 4 parts of 
rosin, 1 of wax, and 1 of turpentine. Apply hot. 

4, For metal upon glass, melt rosin, 40, turpentine, 
3, and plaster of paris, 4. Apply hot. 

D. Cements for Leather. 

1. For cementing leather belts, make a solution of 
good glue (13 test), dissolving 1 part of glue in 4 parts 
of water. Dissolve, separately, 1 part of tannic acid 
in 10 parts of water, adding sufficient glycerine to 
promote solution. Mix the two hot solutions, and heat 
until the mass is stringy. To apply, have the cement 
very hot, roughen the edges of the belts with a file, 
warm them slightly, and the moment the cement has 
been applied, press them well together by means of a 
heavy weight and permit them to dry two or three days. 

2. Gutta-percha, 6 parts; asphaltum, 6 parts; oil of 
turpentine, 1 part. The ingredients are to be carefully 
melted together and the cement applied hot. 

3. For cementing strips of very thin leather, cloth to 
leather, or cloth to cloth, make a solution of elastic 
bands in benzine. This is best effected by filling a 
bottle with the elastic bands, pouring in benzine, corking 
the bottle and subjecting the contents to alternate 
shaking and rest, until solution has been effected. A 
better solution may be made by preparing a solvent of 
1 part benzine and 2 parts carbon-tetrachloride. Such 
a mixture is not only a better solvent for the rubber, 
but possesses the additional advantage that it 1s non- 
inflammable, refusing to ignite even if a lighted match 


162 GLUES AND GELATINE 


is applied directly to it. Chloroform may be used in 
place of the carbon tetrachloride, in the same proportion, 
with equally satisfactory results. 

4. For the purpose of cementing leather to metal, 
the cement for leather belts is useful. The surface of 
the metal should be slightly roughened, and the glue 
spread upon it, after warming the metal. Do not let 
the glue chill. The hot tannin solution is spread upon 
the warmed surface of the leather, which is then pressed 
down upon the metal and held until dry. 

EK. Cement for Wood. 

1. For wood that may not be glued on account of 
exposure to the air, dissolve shellac with as little wood 
alcohol as is necessary to effect solution. 'The cement is 
to be applied to both pieces, and pressed firmly together. 

2. For attaching metal letters to wood, or wood to 
metal, a solution of glue should be incorporated with 
some good varnish, turpentine being used in sufficient 
quantity to effect a proper emulsion. . 

3. A cement for wood, resisting the action of alkalies 
and acids, may be prepared by mixing equal parts of 
rosin, asphaltum, and brick dust, melting these carefully 
together. 

F. Cements for Bone. 

1. For ivory and bone, melt at a low heat 2 parts of 
Japan wax, 2 parts of rosin, and, when these are melted, 
add sufficient turpentine of good quality, to reduce the 
melt to a syrup consistency. 

2. For knife handles, incorporate equal parts of rosin, 
sulphur, and iron filings. This is to be used hot, and 
the knife which is to be cemented to the handle should 
be heated previous to the application of the cement. 


MANUFACTURING RECEIPTS 163 


Flexible Glue and Padding Composition. — This prepa- 
ration is indispensable in the binding of books and in 
the manufacture of writing-pads or tablets. It is used 
also for the manufacture of certain small toys, such as 
the grotesque faces vended by street-fakirs. To pre- 
pare it, select a strong glue, not less than 1 X in test 
and preferably A Extra. It is best to have this thick 
cut, in order that uneven softening may be prevented, 
owing to the fact that the glue has not been evenly wet. 


No. 1. Extra Strona CLEAR COMPOSITION. 


he CSS 9 SS ra 30 parts 
ee oo oy cok in ade oe ge Ow BO 
RureenrreeeayY DOCY)). 20.0 s ete ee eee 2 aa 


The glue is to be softened in the water and then 
melted uniformly at as low a temperature as possible. 
The glycerine is then well stirred in. The melt is to be 
east in shallow pans, from which it may be removed 
when set. This mixture must be preserved by the 
addition of pure crystal carbolic acid, dissolved in a 
little glycerine and water. ‘To disguise the odor of the 
preservative, perfume with some essential oil such as 
rosemary, sassafras, or wintergreen. 


No. 2. Extra Strona Wuite Composition. 


A Extra glue, white (opaque) ...... ay SR AYy rT 30 parts. 
a 16 ee eat ne RP are Ee Pr 50. (** 
Mervoerme (heavy body) ...........c..620ce05; 160" 


The procedure is exactly as above. Same materials 
used to perfume it. 


No. 3. Mepium StTRoNG CLEAR COMPOSITION. 


Le ST ARS Ce kT eR ae eee ey OR ia 


164 GLUES AND GELATINE 


No. 4. Meprum Strona WHITE CoMPOSITION. 


1} opaque ghie- vo. coh sb od ee Ce 30 parts 
Waters. o.5 Shes aaa oe ie ee ee 26 
Glycerine (.5. 2.228. a Gee ies oo te 15/-* 


Nos. 3 and 4 are to be preserved and perfumed with 
the same materials as above. 

Colored Compositions. — Any of the above composi- 
tions may be colored to suit by the addition of some 
aniline or coal-tar color. The white compositions are 
easiest to color and require less coloring material than 
the clear. 

In use, these compositions may be applied direct, or 
may be added to regular glue solutions, in proportions 
to suit. 

Liquid Glues. 


1. Glue not exceeding 13 strength ........... 30 parts. 
Water... 2 o.oo Se 0 50 
Chloride of calcium... ... 5... .4 2 ee LP 


First dissolve the chloride of calcium by boiling in 
the 50 parts of water. Let this solution become cold, 
and then put in the glue to be soaked up. When 
softened, melt the glue and preserve with carbolic acid, 
perfuming to suit. 

2. Prepare a solution of weak glue in its own weight 
of water. To this add an equal volume of strong acetic 
acid, heating for nine or ten hours. If properly carried 
out, this yields a very effective glue for light woodwork, 
as well as mending china ornaments, etc. The persist- 
ent odor of the acetic acid may be partially disguised 
by the addition of some essential oil. 

Box Maker’s ‘‘Liquid Glue.’’ — This contains no glue 
whatsoever, being prepared from three grades of corn- 


MANUFACTURING RECEIPTS 165 


dextrine. To make it, dissolve equal parts of light 
canary corn-dextrine, dark canary corn-dextrine, and 
British gum in sufficient water to make a paste that 
possesses medium fluidity. Preserve with formalde- 
hyde. The dextrines are to be dissolved in boiling 
water, and if the solution is boiled for a couple of hours 
it will thicken markedly. To effect a solution free from 
lumps, the dextrines should first be worked into a 
heavy paste with cold water, the balance of water 
added, and the whole boiled with constant stirring. 

Photo-Library Paste. — This excellent substitute for 
mucilage in sticking paper and invaluable medium for 
mounting photographs, is prepared as follows. The 
white dextrine alluded to is potato-dextrine, known in 
the market as White E. S. or H White. 


No. 1 
RMR IOUT shins st ce se yee es eee en 20 parts 
Ns ya oo ge sgn on ds ge cee cee O09 
RE Fe cis ae pe ee bk aie ce ts 08 2k 


The dextrine is first worked to a cold paste with a 
little water, the balance of water added, and the whole 
heated until perfect solution is effected. The glycerine 
is now added. Some formaldehyde and a very little 
purest carbolic acid are used as preservatives, and 
sassafras or wintergreen as a perfume. The solution is 
put aside for three or four days, when it sets to a firm 
paste. 


' No. 2 
RI RCTEILE Gigs 460 el vet arveiSiaievss Fe(neles ie 10 parts. 
LE EOE SOS se oghatete Moan LO iy te 
IN rpg ecw Pe la a paces wie is a ates Lites 


RT el Potiaiis ee y's  X cals Wo'v elthe'e nema 3 


166 GLUES AND GELATINE 


Same procedure as with No. 1. 

Starch Pastes. — These may be prepared from wheat, 
corn, tapioca, sago, or potato starches. Potato starch 
will yield a paste of heavy body with little adhesiveness, 
whereas that from tapioca is rather fluid and sticky. 
Sago yields a very dark, sticky paste. Corn starch is 
not very useful for paste-making. 

In order that the paste be free from lumps, it 1s essen- 
tial that continual stirring be applied during boiling. 
Starches and dextrines should never be boiled by con- 
tact with the naked flame. The starch, in all cases, 
should be first brought into suspension in cold water, 
the balance of water boiled separately, and the cold 
emulsion of starch added slowly to this. All starches 
require careful preserving in solution. Bichloride of 
mercury, formaldehyde or carbolic acid may be used. 
Hydrofluoric acid is a good preservative, or any one of 
its salts, such as ammonium fluoride. 

Starch pastes are rendered far more adhesive if the 
starch be treated with some agent tending to partially 
hydrolize them. Dilute acids, alkalies, and even chlo- 
ride of calcium, are useful for this purpose. A very 
effective paste from tapioca is made as follows: 


Tapicoa .. ..c0). . ats s ote op oe 20. 
Water .2 55 68 wen eed a + Se ole cee 100. 
Chloride of Calerum .......... es fae ee as 


Pastes of this kind should never be boiled with direct 
steam, as the action of this is entirely too drastic. 
Jacketed heat invariably produces a heavier paste, with 
given proportions, than does direct steam. The addi- 
tion of one fifth of one per cent of nitric acid to the 
paste while it is boiling will increase its fluidity and 


MANUFACTURING RECEIPTS 167 


stick. Similarly, combined sago and tapioca may be 
dissolved in the cold, or with a minimum of heat, by 
the aid of caustic alkalies, to form a very powerful 
adhesive which is a substitute for rubber cement in 
lighter kinds of work. This may be prepared as follows: 


ME Fo Sowiints go Ciens ¢ 8 v oonte ne 10. 
MS ee ds cede s Ce ee nS 10. 
Oe on On He Ae ee a 100. 


Caustic Soda solution, 30° Be. " 


The starches are introduced, with constant stirring, 
into the water, which is at about 80° I’. The caustic 
soda solution is then added little by little, until perfect 
solution is effected. The mixture is now dark and 
strongly alkaline. Nitric acid is now added, in small 
portions at a time, until the mass is Just faintly acid in 
reaction. Stirring to avoid lumps is a most important 
factor throughout the operation. The action of alkali 
and acid tends to destroy the gelatinizing properties of 
the starches, yielding a thickly fluid paste. 
Flour-Paste. — Paste made from wheat flour is in 
ereat demand among. paper-box makers, cigar-box man- 
ufacturers, workers in leather goods, etc., who use it 
either as a label paste, or for the lighter work where 
glue is not absolutely essential. Good flour-paste is 
white in color, very sticky, and still possesses the degree 
of fluidity permitting it to work out smooth. Its 
manufacture is attended by many difficulties, owing to 
the fact that it does not suffice merely to boil up the 
flour in so and so much water, in order to procure a 
working paste, but the action of certain chemicals has 
to be depended upon to produce the result. Accord- 
ingly, the formulas advocated for the manufacture of 


168 GLUES AND GELATINE 


flour-paste are legion. The majority are absolutely 
worthless. 

A great defect exists in paste-making machinery. 
While this is designed to permit uniform agitation of 
the cooking flour and water by means of a worm agi- 
tator, and is even provided with sifting apparatus, 
which is automatically operated by the main agitator, 
paste machines are designed exclusively for direct or 
live steam. This is a great mistake. What has been 
said in regard to starches producing thicker and stickier 
pastes if cooked in jacketed apparatus applies equally 
to flour. So drastic is the action of direct steam, that 
frequently the paste starts to ‘‘go thin” ere all the 
particles of flour have burst. On the other hand, cook- 
ing with direct steam may be inadvertently prolonged, 
as it is difficult to tell just when the paste is ‘‘done,” 
and in this way the paste cools “‘livery.”’ 

Since the paste manufacturer, unless he wishes to go 
to extra expense in procuring special apparatus, has no 
alternative save to use the standard form, with the direct. 
steam, he should always observe the following precau- 
tion. The paste is best cooked by introducing a full 
head of steam, and the instant that boiling takes place, 
as is indicated by the cessation of rattle and the com- 
mencement of rumble, the steam should be almost 
completely cut off. Once a certain degree of heat is 
achieved (practically 200° F.), the flour needs but little 
additional heat, in order that the grains shall burst and 
thus go into solution. Any heat beyond this degree is 
not only superfluous but is likely to spoil the paste by 
over-cooking. 

If the paste is to be prepared in small quantity for 


MANUFACTURING RECEIPTS 169 


household and office use, cooking is best effected in a 
double boiler such as is employed for oatmeal and 
other cereals. Sufficient heat will be established in 
the inner kettle to cook the flour slowly and uniformly. 
For such purpose, 15 parts of flour should be cooked 
with 100 parts of water, which will form a heavy paste. 
The moment the flour has gelatinized, take the boiler 
away from the stove, flame, or whatever supplies the 
heat to the outer kettle, and continue stirring slowly 
until the paste has cooled. 

As to the chemicals used to partially hydrolize the 
starch of the flour in order to increase the stick of the 
paste, none answers so well as chloride of calcium, using 
about 5 pounds to every barrel of paste. If the paste 
were subjected to jacketed cooking, 10 pounds of flour 
in 100 of water, plus 3 pounds of chloride of calcium, 
would produce an extremely heavy and sticky paste, 
which would, nevertheless, work out smoothly. If 
borax is intelligently used, a good paste results with a 
minimum of flour. Such pastes are rather dark in color, 
however, owing to the action of the alkali upon the 
gluten of the flour. If too much borax is used, the 
paste will decay quickly, previously becoming lumpy. 

The commonest method of hydrolizing the starch of 
flour paste is to use hydrochloric acid. In this the 
necessary quantity of bichloride of mercury, for preserv- 
ative purposes, is first dissolved. This is then added 
to the cold mixture of flour and water in the machine, 
and cooking is begun. For two barrels of paste a 
pound of acid containing 4 ounces mercuric chloride 
will answer. 

In order that the paste shall not go livery, it is neces- 


170 GLUES AND GELATINE 


sary that it be stirred slowly for a while after it is done, 
to rid it of all excess of steam. It is advisable to let 
it run in a thin stream from the machine into a tank, 
equipped with agitator, some distance below. On no 
account should the paste be stirred rapidly for cooling 
purposes. This will cause it to go thin. 

Paste preservatives are fairly numerous, formalde- 
hyde, carbolic acid, salycilic acid, bichloride of mercury 
(corrosive sublimate), and hydrofluoric acid’ answering 
the requirement. The first two are barred because of 
their characteristic pungent odors, the second on 
account of its expense, while the use of the last named 
is always attended by danger owing to its fearful corro- 
sive properties. It is a good preservative, however, 
and if carefully handled does good work. On the whole, 
bichloride of mercury is the best and easiest to use. 

No treatise on paste-making could be exhaustive in 
character. Success depends in a large measure upon 
experience, and the observance of precautions that are 
learned only through experience. The above hints, 
however, should prove helpful. 

Gum Tragacanth Paste. — Gum tragacanth possesses 
the property of absorbing water to many times its 
weight and is thus converted into a paste. No heat is 
required in its preparation if ordinary precautions are 
observed. A serviceable paste may be made by cover- 
ing 10 parts of good quality tragacanth with 200 parts 
of water and allowing the gum to swell. The addition 
of a small quantity of glycerine adds flexibility to the 
paste, which must also be adequately preserved against 
decomposition or souring. 

Dextrine Mucilage. — A fairly good quality of muci- 


MANUFACTURING RECEIPTS 171 


lage may be prepared by simply dissolving certain 
dextrines in very hot or boiling water.. Potato or 
tapioca dextrines are best adapted to the work. About 
30 parts of dextrine, dissolved in 100 parts of water, 
will make a good thick mucilage. This must be pre- 
served with formaldehyde and carbolic acid, the odors 
of which may be disguised with a little essential oil. 

Dextrine mucilages are usually too dark in color 
unless a very pale dextrine is selected. The one giving 
the best results is ‘‘canary white” potato-dextrine, 
which is imported from Germany. Canary-dextrine 
(potato) yields a somewhat darker shade of mucilage. 
These mucilages are improved by the addition of about 
3 per cent of acetic acid, and some glycerine to impart 
flexibility and prevent “‘cracking”’ of the dried mucilage. 
Envelope gums are prepared practically upon this prin- 
ciple, either from tapioca or potato dextrines, and at 
times from mixtures of both. 

Gum Arabic Mucilage.— This is usually paler and 
clearer than dextrine mucilage. A good, clean grade 
of gum should be selected, as otherwise the product 
will contain particles of dirt and fine straws. Twenty- 
five parts of gum arabic are put to soak over night with 
75 parts of clean water, in a copper jacketed kettle. 
When the gum is sufficiently softened, it is dissolved 
with the aid of heat. About 10 parts of glycerine are 
added in which has been dissolved 5 parts of pure 
earbolic acid. When somewhat cool, oil of wintergreen 
is added to disguise the odor of the carbolic. 

Prepared Size. — A size of some sort 1s necessary to 
correct distemper of walls before they are calsomined 
or painted. At times a good glue suffices for the pur- 


172 GLUES AND GELATINE 


pose. At others, substances such as chalk, whiting, and 
even clay are mixed with the glue. To increase the 
efficacy of the size, soap and alum are frequently added, 
it being assumed that the soap promotes the “slip” 
in application. A sample of such size, analyzed by 
the author, contained: 





Chalk 2 jo s.. ae 2-08 iyi eg aie a er 80 parts. 

Glue, finely powdered »............ sn 5 see 10° "S 

DNs ae M EAI eee ay hye 

Soap (in the form of powder) ................ ee of 
100. 


Special Gums. — Certain sizes or gums for stiffening 
are used in shoe manufacture. Of these, the “‘box-toe 
gum’ is a prominent example. The following are for- 
mulas of preparation: 


No. 1. 
Light canary corn-dextrine . 5.7). <.25 #eee 10 parts 
Tale). 2 sce nen ie pls es 2 1Dees 
Oxide of Zine . . 2... 4.2... tn be ry BS 2 
China clay .. 0... 60.5% cs a ee ee 1G: 
Water 1. conics eee athens ef oe ee ee ou tees 
No. 2. 
Chalk 000 bia stg et soo cs 15 parts. 
Ground mica (80 mesh). = .5 4.1... oe thee 
Light. canary corn-dextrine: +... .... 4.2) eee 45 * 
Water .. 5.00. G0 .85 a 35 CO 


In both the above a little more water than is specified 
should be used to dissolve the dextrine, and into this 
solution, which is apt to be heavy unless very hot, are 
worked the other ingredients, a little of each at a time. 
The result is a paste or gum of great consistency. 


CHAPTER X 
ANALYTICAL OPERATIONS 


WuiLE not at all averse to consulting a qualified 
chemist when need of his services arises, progressive 
superintendents frequently desire to carry out for them- 
selves the simpler analytical operations, if only that they 
may thereby better comprehend the import of the 
chemist’s work. In the interest of such, it has been 
deemed advisable to add to this work a limited exposi- 
tion of analytical technique. No attempt is made to 
outline quantitative processes save such few as pertain 
to the standardization of solutions; nor is it to be ex- 
pected that the perusal of this chapter will enable the 
inexperienced to qualify as expert analysts. For the 
details of specific determinations, the reader is referred 
to any one of the many excellent works extant upon the 
subject of quantitative analysis.‘. Since, however, the 
success of analytical operations is largely subject to 
the rules of common sense, if the reader will combine 
the instructions for a specific determination with the 
- suggestions as to technique herein embodied, fairly 
accurate results should be obtained. All analytical 
work presupposes the greatest care in execution, lest 
errors of manipulation creep in to invalidate the result. 

1In connection with this chapter and the Appendix, the reader 


wil do well to consult Olsen’s Quantitative Analysis. 
173 


174 GLUES AND GELATINE 


Apparatus Required. — The following apparatus is 
essential to the proper execution of the majority of 
investigations pertaining to glue and gelatine. 

1. A good balance for weighing, provided with an 
accurate set of weights. The balance should be sensi- 
tive to at least one milligram (1—28000) ounce. Bal- 
ances of precision, sensitive to 1-10 milligram, are best. 
These, as a rule, are costly, and instruments less sensi- 
tive will supply results correct within technical limits. 

2. A drying oven. This may be of block tin, or 
better, copper-jacketed. 

3. A copper water-bath fitted with concentric rings. 

4. Assorted Erlenmeyer and Florence flasks. 

5. Two burettes, 50 c. c., graduated in tenths, with 
glass stop-cocks. 

6. Volumetric pipettes, 10, 25, and 50 c. c. capacity. 

7. A 100 c. c. graduated cylinder. 

8. A 10 c.c. pipette, graduated in 1-10 ¢. ¢. 

9. Glass funnels of various diameters. 

10. Watch- and clock-glasses, assorted sizes. 

11. Filter paper, Swedish, 1 F, assorted diameters. 

12. Sohxlet extraction apparatus, medium size, com- 
plete with flask and condenser, also capsules to fit. 

13. Test-tubes, 6 inches long, 1-2 inch diameter. 

14. Beakers, Griffith’s shape, several nests. 

15. Assorted glass and porcelain evaporating dishes. 

16. Two separatory funnels, 300 c. c. and 500 ec. ec. 

17. A short piece of platinum wire and a small square 
of platinum foil. 

18. Several Bunsen burners, tripods Ae, ringtones 

19. Squares of iron wire gauze for tripods. 

20. Glass stirring-rods and assorted glass tubing. 


ANALYTICAL OPERATIONS 175 


21. Volumetric flasks for the preparation of stand- 
ard solutions. Sizes, 100 c. c., 250 c.c., 500 ¢.c., and 
1000 ec. ec. (1 liter). 

22. Half a dozen porcelain crucibles, Royal Berlin, 
No. 00, with covers. 

23. A platinum crucible, 15 grams. 

24. A platinum evaporating dish, 15-20 grams. 

25. A desiccator, chloride of calcium variety. 

26. A gas blast-lamp, with adequate bellows. 

Reagents. — The reageants required are those com- 
monly employed in qualitative work, a list of which will 
be found in the appendix. 

Analytical Processes. _ 

1. Desiccation. —'The case in which the balance is 
placed must be kept absolutely dry, lest hygroscopic 
substances, in the course of weighing, absorb moisture 
therefrom. Not only this, many substances, previous 
to weighing, must be heated to expel moisture and then 
cooled in a perfectly dry atmosphere. For maintaining 
the balance case in a dry condition, a small glass vessel 
should be filled with pure, granular chloride of calcium, 
and this vessel kept constantly in the case. The chloride 
of calcium must be renewed from time to time. For 
cooling objects and substances to be weighed, the desic- 
cator is employed. The lower chamber of this is filled 
with granular chloride of calcium. A partition separat- 
ing the upper chamber from the lower, which serves also 
as a platform on which to rest objects, is made by affix- 
ing corks of uniform size to the four corners of a piece 
of wire gauze that has been fitted to the dimensions of 
the chamber. Holes may be cut in this to accommodate 
crucibles. The lid of the desiccator should be slightly 


176 GLUES AND GELATINE 


greased with vaseline, to insure perfect contact with 
the ground edge of the upper chamber. 

All porcelain apparatus should be heated over the 
Bunsen flame for at least fifteen minutes before intro- 
duction into the desiccator. In many instances it is 
advisable to subject the object to the blast flame as 
well. Porcelain requires at least twenty minutes’ cool- 
ing in the desiccator. Platinum will require ten minutes’ 
heating and fifteen minutes’ desiccation. 

2. Weighing. — That the hfe and usefulness of the 
instrument may be prolonged, certain simple precau- 
tions are to be observed in connection with the use of 
a balance. Before any attempt is made at weighing, 
it should be seen that the instrument is perfectly level. 
It should rest on a table of such height that the ivory 
scale is at the level of the eyes when the operator is 
seated before the table. The balance should never be 
exposed to direct sunlight nor to the fumes of the labora- 
tory, nor should it be kept in too close proximity of any 
source of heat lest this cause undue expansion of any of 
the parts. It should be kept scrupuously clean, the 
scale-pans being dusted with a fine camel’s-hair brush. 
Under no circumstances should oil be applied to any 
part of the balance; proper cleaning, from time to time, 
of the various parts will insure the perfect working of 
the instrument. In releasing the pan-rests or beam, 
care must be taken not to jolt the apparatus unneces- 
sarily. Nothing will ruin a sensitive instrument so 
quickly as the too sudden arrest of its oscillation. 

Methods of Weighing. — The importance of accu- 
racy in the use of the balance cannot be over esti- 
mated. The slightest error in weighing out the original 


ANALYTICAL OPERATIONS LAG 


sample or the final precipitate from which some con- 
stituent element of the sample is to be deduced, will 
invalidate the analysis no matter how carefully inter- 
mediate operations may be conducted. Objects to be 
weighed should be at the same temperature as that 
obtaining in the balance-case. Hence the desiccator 
should be kept next to and under the same conditions 
as the balance. Hot, or even warm, objects should 
never be placed upon the scale-pan, for, not only will 
the heat emanating from them cause the expansion of 
certain parts of the balance, rendering the instrument 
worthless for the time being, but the objects themselves 
will increase in weight as they cool. 

Even though in apparant equilibrium, the zero or 
position of rest of a balance is never exactly at the zero 
mark of the scale. ‘T’o assume that such is the case, is to 
sacrifice a degree of accuracy in weighing. The most 
accurate method of weighing presupposes the deter- 
mination of the true zero or position of rest, and that 
weight which will restore this position of rest is the true 
and final weight of an object. 

The method of weighing to be adopted will depend 
upon the sensitiveness of the balance at hand. If this 
does not exceed one milligram, it will suffice for all ordi- 
nary purposes to weigh by the simple expedient of plac- 
ing the properly desiccated and cooled object on one pan, 
and adding weights to the other until equilibrium is re- 
stored. If such balance has been correctly set up, and is 
kept under conditions where it is not affected by vi- 
bration or other undue influence, the position of rest will 
remain practically at the zero line of the scale and any 
slight deviation will be offset by errors in the weights. 


178 GLUES AND GELATINE 


Such a balance will not permit of weighing closer than 
one milligram or to third decimal place. 

On the other hand, if the balance be one of great 
precision, weighing to tenths of milligrams, the position 
of rest is far more variable, and cannot be assumed to 
be at the zero line of the scale unless the needle has been ~ 
deliberately adjusted to the latter mark. Even then, ~ 
the position of rest will remain constant but for a short 
time under the most favorable conditions. 

Determination of the Position of Rest. — Each of the 
ten scale divisions on either side of the dividing line is 
mentally further divided into tenths. Swings of the 
needle to the right of the dividing line are arbitrarily 
designated positive or +, and those to the left, nega- 
tive or —. The balance is set in motion and the plus 
and minus swings noted. Let us assume that these are 
as follows: } : 


+ 10 (to the right of the dividing line). 
— 8 (to the left of the dividing line). 
aie 3 

—7 

arte 


The first pair of swings indicates that the needle 
oscillated further to the right than to the left, by two 
seale divisions. The oscillation would be of the same 
proportional value, though of smaller amplitude, had the 
needle started at the dividing line, traveled two scale 
divisions to the right, and then returned to the dividing 
line and stopped. Were the balance in equilibrium, this 
would correspond to a swing of one scale division on 
either side of the dividing line. It will at once be seen 


ANALYTICAL OPERATIONS 179 


that one scale division equals halj the difference between 
the first two swings. Similarly the half-differences be- 
tween the remaining swings or oscillations are 0.50, 1, 
and 0.50. ‘These are designated as positive or +, since 
the swing to the right of the dividing line was in each 
instance of greater amplitude than that to the left. 
Continuing our hypothesis, the tabulated statement of 
results at this stage is: 


HALF-DIFFERENCE 





+ 10 
= 8.= 7 1.00 
ob a ot 0.50 
Sa Ray, 
+ 8 = + 0.50 
4) + 3.00 
+ 0.75 


By dividing the sum of the half-difference by 4, the 
number of such half-differences, we learn that the po- 
sition of rest of the balance for this determination is 
0.75 of a scale division to the right of the dividing line 
of the scale. Five such determinations as the above 
should be made and the arithmetical mean of the result 
taken as the position of rest. 

Extension of the above procedure enables us_ to 
determine the delta of our balance. This means the 
milligram equivalent of each scale division. To do this, 
we determine the position of rest as above. The rider 
is now placed. at the 1 milligram mark on the beam, and 
the position of rest determined under these conditions. 
This time it will be negative or —, as the weight causes 
the needle to swing further to the left than to the right. 


180 GLUES AND GELATINE 


Let us assume that the position of rest, as first deter- 
mined, is +0.75; and that, with the weight, it is —1.25. 
If we subtract these two algebraically we find the differ- 
ence to be two scale divisions. That is, the difference 
of position of rest, due to the milligram weight, equals 
two scale divisions. Hence the milligram equivalent of 
one scale division is found by dividing 1 milligram by 2. 
The figure so obtained, 0.5 mg., is the so-called delta of 
the balance. This changes about once per month, under 
normal conditions, and more frequently if the balance 
be exposed to undue influences. The function for the 
figure for delta in weighing operations will be seen from 
the following. 

Weighing by Half-Differences. — In its entirety, the 
process of weighing by swings necessitates the deter- 
mination of the initial position of rest, which, let us 
say, 1s + 0.75. The object is then placed upon the pan 
and weights added to three decimal places. Assume 
that the weight thus far is 9.542. We have now to 
determine what weight will restore the balance to the 
original position of rest. To do this, we again determine 
the position of rest, and this, for example, is found to 
be +1.25. The difference between this and the original 
is 0.50 scale division. Since each scale division is equiva- 
lent to 0.5 milligram (delta), we require the additional 
weight of 0.25 milligram to restore the balance to the 
original position of rest. We accordingly add this weight 
or rather 0.3 milligram (since our balance does not weigh 
to hundredths) and once more determine the position 
of rest. If this proves to be + 0.75, the final weight of 
our object is 9.5423 gram. 

It may be objected that the process of weighing by 


ANALYTICAL OPERATIONS 181 - 


swings consumes too much time, and the latter is as- 
suredly a factor in chemical analysis. True, the novice 
will find the method tedious, until he has had consider- 
able practice. At the same time, the importance of 
accustoming himself to accurate methods of weighing 
cannot be too strongly urged, provided he has equipped 
himself with a sensitive instrument. 

Less troublesome and tedious is the method of weigh- 
ing by halj-differences, a method that presupposes that 
the position of rest of the balance is always at the zero 
or dividing line of the scale. That such is not the case 
with an instrument of great sensitiveness has already 
been pointed out, and the reliability of the method will 
depend, first, upon the maintenance of the balance under 
strictly uniform conditions, and, secondly, upon the ad- 
justment of the needle to the zero of the scale each 
morning before starting work. This done, it will be 
necessary to let the balance rest for an hour before 
attempting to use it, in order that conditions of tem- 
perature, etc., become normal. Before attempting this 
adjustment, it should be first seen whether any deviation 
from the adjustment of the previous day has taken 
place. If not, there is no need of readjustment. These 
precautions observed, the method of half-differences be- 
comes satisfactorily reliable and possesses the advan- 
tage over the complete oscillatory method, in that it 
consumes far less time, a weighing being accomplished 
in five minutes with reasonable practice. In operation, 
the method is as follows: 

An object is being weighed, and the operator has 
already placed upon the pan 9.542 gram. The balance 
is now set in oscillation and the swings to right and left 


182 GLUES AND GELATINE 


of the dividing line noted. These, let us say, are 8 scale 
divisions to the right and 6 to the left. The difference, 
+ 2, shows that the weight is still deficient. The weight 
required is that which will cause the needle to swing 
one scale division on either side of the dividing line. 
One scale division is seen to be half the difference be- 
tween the swings +8 and—6. We have already 
determined that the milligram equivalent of our hypo- 
thetical balance is 0.5 milligram. Hence, if this weight 
be added by means of the rider, we shall find that the 
balance is restored to equilibrium, oscillating equi- 
distantly on either side of the dividing line. The final 
weight of the object is thus 9.5425. 

The novice is at times troubled by the failure of the 
needle, when the beam is first released, to oscillate on 
both sides of the dividing line. This difficulty may be 
overcome by causing a gentle draft to impinge on the 
right pan by gently waving the hand toward this pan. 
It is well to adopt this practice at all times, disregard- 
ing the first pair of oscillations and relying on the third 
for the reading. Thus, if after stimulating the motion 
of the balance as suggested, the swings are 


+9 +74 +7 
—~6 —5} —5, 


we take the half-difference between the third pair, viz., 
one scale division for our calculation, and multiply this 
by the delta to determine the final weight required to 
restore the balance to equilibrium. 

Preparation of Samples for Weighing. — Substances 
to be analyzed are, as a rule, dried prior to weigh- 


ANALYTICAL OPERATIONS 183 


ing out the initial sample or samples. Save such as 
would lose water of crystallization by crushing, they 
are first reduced in a mortar to an impalpable powder 
and then placed in the oven until all moisture has been 
expelled. The temperature of drying will depend upon 
the nature of the substance. Much importance at- 
taches to the method of transferring the dried substance 
to the weighed container in ‘weighing out.” The 
practice of first weighing crucible or other container 
and, as this rests upon the scale-pan, introducing the 
substance by means of a spatula, is a simple and con- 
venient one, but requires great care lest any substance 
be spilled onto the pan with the result that the sample 
in the crucible, etc., is less than the weight recorded. 
It were better for the novice, once he has weighed the 
container, to remove this from the balance and, placing 
it on-a clean sheet of paper, introduce the substance 
and proceed to the second weighing. The removal and 
replacement of the container must be effected by means 
of a pair of tongs. Under no circumstances should 
contact of container with the hand be permitted. 
Where the sample is to be placed in containers either 
too large or too heavy for the balance, the following 
method of weighing out will be found convenient. As 
the substance is drying in the oven, a test-tube, fitted 
with a smooth, tight cork should be dried at the same 
time and the substance subsequently introduced into 
the tube. This is then corked and placed in the des- 
iccator to cool. Before weighing, the tube is permitted 
to rest in the balance case for fifteen minutes. The 
container, into which the sample is to be weighed, is 
placed near at hand upon a sheet of black glazed paper. 


184 GLUES AND GELATINE 


The tube plus cork and contents is carefully weighed, 
then uncorked and a little of the contents shaken into 
the container. A piece of bibulous paper is employed 
to handle the tube and cork to avoid contact with the 
hand. The tube is recorked, permitted to rest a few 
minutes in the balance case and again weighed. The 
difference in weight represents the sample taken. If, 
inadvertently, any particles of the sample have fallen 
upon the paper, these may readily be added to the main 
portion within the container. Two samples require but 
three weighings by this method. The weighings are 
best noted as follows: 


Tube + cork + substance = 10.8976 
Tube + cork + substance — 10.6543 


Sample taken = __.2433 gram 





This is better expressed as 243.3 milligrams. For a 
second sample, we might then have 


Tube + cork + substance = 10.6543 
Tube + cork + substance = 10.4321 


Sample taken = 222.2 mgs. 


It is advisable always to express the weights taken in 
milligrams and to base all subsequent calculations on 
milligrams. 

In order that the results may be controlled, it is cus- 
tomary to run duplicate samples and these should 
approximate each other in weight. Where the analyst 
has at his command a sensitive balance, large samples — 
should never be taken for analysis. A large sample 
means subsequent bulky precipitates awkward to handle 


ANALYTICAL OPERATIONS 185 


and entailing mechanical loss in washing. On the 
other hand, it must be remembered that, with a small 
sample, each loss through faulty manipulation counts 
more than with a large sample. The analyst must 
regulate the sample taken through his knowledge of 
the properties of the substance sought. Where he 
suspects a constituent which he knows will yield a bulky 
precipitate, the minimum working sample should be 
weighed out; and vice versa, since there is added safety 
in large samples. 

Weighing out Liquids. — For this, a weighing bottle, 
provided with ground stopper, should always be em- 
ployed. It will save time if a lead counterpoise is made 
for this bottle and subsequently used to tare the bottle 
in weighing. 

In weighing potash bulbs of any description, they 
must be permitted to rest for a time in the balance case 
that the contents may acquire the temperature obtaining 
therein. This applies equally before and after absorp- 
tion of carbon dioxide. 

Calcium chloride tubes that have been employed for 
the absorption of moisture should be accorded the same 
treatment. | 

Filtration. — Separation of filtrates and precipitates 
entails certain precautions, neglect of which will seri- 
ously hamper the operation. In selecting funnels, only 
those with long, narrow stems and flawless sides should 
be accepted. Such will permit of rapid and uniform 
filtration. Some precipitates, because of their fineness, 
require double filters. In preparing the filter, the paper 
is folded in half, and this again in half, taking care that 
the edges are even. It is now a quadrant. Opening 


186 GLUES AND GELATINE 


the filter again to semi-circular form, a small piece is 
torn from one end of the diameter. This subsequently 
serves, after moistening with alcohol, to detach any par- 
ticles of dry precipitate adhering to the funnel itself, 
in which case it is incinerated with the main filter. 
After detaching the portion of paper, the filter is once 
more folded to a quadrant and inserted into the per- 
fectly clean and dry funnel, conforming its shape to that 
of the latter by pressing, care being taken not to rup- 
ture the point. One side of the filter represents a single 
thickness of paper and the other. three thicknesses. If 
a double filter is required, a second paper is prepared 
in the same manner as the first and introduced into the 
funnel superimposed upon the first paper in such way 
that both sides of the complete filter represent four 
thicknesses of paper. Whether single or double, the 
filter, after conforming its shape to that of the funnel, 
is moistened with boiling water and firmly pressed into 
the funnel to expel all air bubbles between it and the 
surface of the funnel. Let boiling water pass several 
times through the filter, and note if the stem of the 
funnel holds the column of water, free from air bubbles. 
A well-made filter is in reality a miniature air pump. 
Filtration will never proceed rapidly nor efficiently 
unless the stem of the funnel holds the column of water. 
In filtering precipitates, a glass rod is held against the 
lip of the beaker, the end of the rod directed to the 
center of the filter. Under no circumstances should 
liquids for filtration be poured onto the filter direct. 
The filter should never be filled to its capacity, as in © 
this way much precipitate collects at the edges and 
difficulty in washing ensues. The bulk of the precipi- 


ANALYTICAL OPERATIONS 187 


tate is washed from the beaker down the rod, into the 
funnel. | 7 

Washing Precipitates. — Before drying, precipitates 
must be washed free of the precipitating medium, else 
this dries with them, augmenting the weight and pro- 
ducing a fallacious result. Save in certain specific 
analyses, the washing is effected with distilled water, 
which is delivered from a wash-bottle equipped with a 
fine-pointed nozzle attached to the main delivery tube 
by a short piece of rubber tubing, enabling the operator 
to direct the stream at will. Care must be taken to 
wash the edges of the filter, it being customary to wash 
the precipitate down from the sides of the filter towards 
its apex. It must be remembered that many precipi- 
tates are not wholly insoluble in water and hence only 
a minimum of wash-water may be employed. Never- 
theless, washing must be complete. 

In many instances, filtration is effected by holding 
back as much of the precipitate as possible, by means 
of the rod, and washing the precipitate in the beaker, 
bringing the washings and a little of the precipitate each 
time on the filter and washing the latter in between. 
The bulk of the precipitate is finally brought upon the 
filter by means of a stream from the wash-bottle, aided, 
perhaps, by a trimmed feather or rubber “policeman,” 
and the filter given a final washing. This method is 
known as “‘ washing by decantation.” 

Certain precipitates attach themselves to the sides 
of the beaker, and are difficult of removal. For de- 
taching these, a trimmed Guinea fowl feather is most 
useful. The feathers are stripped in toto from one 
side of the shaft, and the balance cut down short with a 


188 GLUES AND GELATINE 


scissors. Where a feather of this description is em- 
ployed, it must be rinsed thoroughly lest precipitate 
adhere to it and loss thus occur. Another aid in rinsing 
beakers of precipitates is the “policeman.” ‘This con- 
sists of a short piece of rubber tubing, of the same 
diameter as the stirring rod to which it is attached by 
slipping over the end of the rod. One end of the rub- 
ber tube is firmly sealed. To be at all serviceable the 
‘‘ policeman ’’ must be perfectly smooth. 

Drying Precipitates. The washed precipitate is 
now dried. The funnel, still retaining the wet filter, is 
covered so as to exclude dust and placed in the drying- 
oven, the temperature of which should not exceed that 
of boiling water. 

Incineration of Filters. — Before the dried precipi-’ 
tate can be weighed, it must be detached from the 
filter and the latter burned to an ash. The weight of 
this ash (which is usually recorded on the package of 
filter paper) is then deducted from the total. The 
entire operation is one of great nicety. The crucible, 
in which the precipitate is to be placed for incineration 
and weighing, is itself desiccated, cooled, weighed, 
and then placed upon a sheet of black glazed paper. 
The funnel containing the filter with dried precipitate 
is uncovered, the filter removed and inverted upon a 
clean watch-glass. By gentle tapping, the bulk of the 
precipitate is freed from the paper. If any has adhered 
to the funnel, the strip of paper originally torn frem the 
filter is moistened with alcohol, and the funnel wiped 
with this, which is subsequently incinerated with the 
main filter. The precipitate detached from the filter 
as far as possible, the latter is folded, the apex placed 


ANALYTICAL OPERATIONS 189 


in the flame until it is ignited and the whole rapidly 
introduced into the crucible which is supported on a 
triangle. The ignited filter is permitted to burn of its 
own accord, and as soon as it smolders a small flame 
is placed beneath the crucible. If this causes the half- 
burnt paper to burst into flame again, remove the Bun- 
sen flame until the former has again died out. As soon 
as the filter is thoroughly charred, and no longer burns 
of its own accord, replace the Bunsen flame beneath the | 
crucible and gradually raise the flame until all carbon 
is burned off, leaving a good white ash. The crucible 
is now cooled, and the bulk of the precipitate is added, 
care being taken to brush the surface of the watch-glass, 
as well as that of the glazed paper, with a feather, any 
particles of precipitate adhering to either being trans- 
ferred in this way to the crucible. The precipitate is 
now ready for simple ignition or prolonged blasting, 
as the conditions demand. 

Volumetric Processes. — Volumetric processes involve 
the use of graduated flasks, cylinders, pipettes and bu- 
rettes. ‘The success of such processes depends upon con- 
sistency in reading the instruments, as well as upon 
their preservation in the utmost state of cleanliness. 

(a) The Pipette. — A description of the use of this 
instrument for a specific purpose will be found under 
the discussion of Viscosity, in Chapter 2. The pipette 
is most convenient for delivering definite quantities of 
liquid, but its proper use presupposes certain precautions. 
As remarked, the instrument must be scrupuously clean, 
lest globules of the discharged liquid adhere to the glass. 
The last drop may be discharged by placing the index 
finger of the right hand over the aperture of the upper 


190 GLUES AND GELATINE 


tube, holding the body of the instrument in the palm of 
the left hand, when the natural heat of the hand will 
cause the air to expand, driving out all liquid. Unless 
this practice is observed, the full capacity of the pipette 
is not delivered and an ultimate error of analysis results. 

(b) The Burette. — Many substances are analytically 
determined while in solution or “volumetrically” rather 
than gravimetrically —7.e., by precipitation and weigh- 
ing. For example, if the strength of an acid solution 
be known, — that is, if we know the exact amount of 
acid contained in each cubic centimeter, and if, further, 
10 c. c. of this solution are required to neutralize x ¢. c. 
of an alkali solution of unknown strength, from the data 
at hand we may readily determine the strength of the 
alkali solution. Such analytical process is termed 
“Titration”; and in the above instance, we speak of 
titrating the alkali against acid. 

The instrument employed for titration is the burette, 
which consists of a stout, long glass tube, provided at 
one end with a glass stop-cock or a rubber tube fitted 
with a pinch-cock. The tube is graduated up to 50 ¢. c., 
each subdivided into tenths. The correct reading of a 
burette presupposes considerable practice. The menis- 
cus, or heavy stratum of liquid at the top, common to 
all columns of liquids, is the guiding point, where no 
“float”’ is at hand to assist the reader. The meniscus 
will be seen to consist essentially of three distinct lines, 
upper, lower, and a very dark line between. Any of 
these may be employed as the guiding line in the read- 
ing; but it behooves the operator to read from the same 
point throughout any one titration or set of titrations. 

As in gravimetric, so in volumetric analysis, dupli- 


ANALYTICAL OPERATIONS 191 


cates are run for the purpose of checking the results. 
Duplicates must be titrated under identical conditions 
of temperature and concentration, if concordant results 
are to be obtained. Each should contain the same 
amount of indicator. 

The flow of solution from a burette should be so 
regulated that 10 c. c. are discharged per minute, or 
the entire contents of the burette in five minutes. If 
discharged with greater rapidity, some drops of solution 
tend to adhere to the upper portions of the tube, and 
‘unless the operator waits for these to flow down to the 
level of the column before taking the reading, this will 
be incorrect. 

(c) Graduated Cylinders. — The correct reading of a 
column of water contained in a graduated cylinder is 
dependent upon the identical principles obtaining with 
the burette. The cylinder is not reliable for measuring 
liquids in analyses presupposing quantitative accuracy. 

(d) Volumetric Flasks.— These flasks, usually of 100, 
250, 500 and 1000 c. c. capacity are accurately gradu- 
ated and are most useful, not only for the preparation 
of standard solutions, but for measuring liquid samples, 
for which latter purpose they should always substitute 
the graduated cylinder. In adjusting the contents to 
the graduated mark on the neck of the flask, the operator 
has to observe the same precautions governing the 
reading of the burette. Liquids, while hot, must never 
be adjusted to the mark, as shrinkage occurs through 
cooling. 

Cleaning Volumetric Apparatus. — A solution of al- 
cholic potash is an excellent medium for cleaning all 
glassware. This need not necessarily be concentrated 


192 GLUES AND GELATINE 


and may be prepared by dissolving about 10 grams of 
dry, chemically pure caustic potash in 100 ec. e. of 80 
per cent alcohol with the aid of heat. The solution 
should be kept in a dark bottle sealed with a tuft of cot- 
ton in preference to a cork, and may be used repeatedly 
for cleansing purposes until exhausted. The apparatus 
cleansed by its use should be subsequently rinsed with 
pure, distilled water and inverted to drain. 

Equally efficacious, and less expensive, is a solution 
of potassium dichromate in concentrated sulphuric acid. 
Such solution may be prepared either by making a con- 
centrated aqueous solution of the dichromate and cau- 
tiously adding an excess of concentrated sulphuric acid, 
or dissolving the salt in the acid direct. Its use is 
governed by the same precautions applying to alcoholic 
potash. 

It is at times inexpedient to rinse burettes and pipettes 
with water, since, unless the apparatus be subsequently 
dried, the strength of a standard or other solution will 
be altered by admixture with the water remaining. 
Burettes, when not in use, may be kept filled with dis- 
tilled water and well corked to exclude dust. When 
it is desired to use the apparatus, this water may be 
run off and the instrument rinsed with about 20 ec. ce. of 
the solution with which it is to be filled. This is then 
run off and the main solution added. 

Pipettes and volumetric flasks, after cleaning, rinsing 
and draining, may be dried by rinsing with alcohol to 
remove the balance of water, then with ether to remove 
the alcohol. The ether is then removed by suction, 
either of the lips or pump. | 


APPENDIX 


The following are the reagents required for the gen- 
eral qualitative and quantitative operations: 


Ammonium acetate. — To 500 c. c. aqua ammonia, add 600 c. ec. 
glacial acetic acid. 

Ammonium carbonate. — Dissolve 50 grams of the salt in 250 
c. c. water and add 25 ¢. c. aqua ammonia. 

Ammonium Chloride. — Make a 10 per cent solution. 

Ammonium hydroxide. — Mix equal parts of concentrated aqua 


ammonia and distilled water. 

Ammonium molybdate. — Dissolve 25 grams of the salt in 100 
c. c. water with the aid of heat. Prepare a mixture of 300 
c. ec. concentrated nitric acid and 200 c. c. water. Mix the 
two solutions with constant stirring. 

Ammonium oxalate. — Make a ten per cent solution. 

Ammonium sulphide. — Pass sulphuretted hydrogen gas through 
aqua ammonia until the latter is saturated and add an excess 
of aqua ammonia. 

Ammonium sulphide (yellow). — To some ammonium sulphide as 
prepared above, add sufficient sulphur to impart a decided 
yellow color when thoroughly dissolved. 

Ammonium sulphate. — Make a 10 per cent solution. 

Barium chloride. — Make a 2 per cent solution. 

Barium hydroxide. — Make a 5 per cent solution. 

Calcium hydroxide.—Stir 10 grams of burnt lume in 100 c. c. of 
water for several hours. Let settle and pour off the super- 
natant solution. 

Ferric chloride. — Make a 10 per cent solution. 

Ferrous sulphate.—To a 20 per cent solution add 2 per cent 
sulphuric acid and a few tacks. 

Lead acetate. — Make a 10 per cent solution and add 1 per cent 
acetic acid. 

193 


194 GLUES AND GELATINE 


Magnesia mixture.— Dissolve 40 grams magnesium chloride, and 
100 grams ammonium chloride in 500 c¢. c. water. Add 25 
c. c. aqua ammonia. 

Mercuric chloride. — Make a 5 per cent solution. 

Potassium acetate.— Make a saturated solution. 

Potassium chromate.— Make a 10 per cent solution. 

Potassium ferricyanide.— Make a 2 per cent sofution. 

Potassium ferrocyanide.— Make a 2 per cent solution. 

Potassium sulphocyanide.— Make a 10 per cent solution. 

Silver nitrate.— Make a 5 per cent solution. 

Silver sulphate.— Make a saturated solution. 

Sodium acetate. — Make a saturated solution. 

Sodium carbonate.— Make a 25 per cent solution. 

Sodium hydroxide.-— Make a 10 per cent solution. 

Sodium phosphate. — Make a 10 per cent solution. 

Sodium sulphide.— Pass sulphuretted hydrogen through a 10 per 
cent solution of sodium hydroxide, and to each liter of 
solution add 50 grams of sulphur. 

Acid acetic.— Add 2 parts of water to 1 part glacial acetic acid. 

Acid nitro-hydrochloric (aqua regia).—Mix 3 parts concen- 
trated hydrochloric acid with 1 part nitric acid. 

Acid hydrochloric.—(a) Concentrated, specific gravity 1.12; (b) 
Dilute. Mix 1 part concentrated acid with 4 parts water. 

Acid nitric.— Two solutions required, one concentrated and one 
dilute (1:4). : 

Acid sulphuric.—Two solutions required, one concentrated and 
one dilute (1:4). 

Acid chloroplatinic.— Make a 10 per cent solution. 

Hydrogen sulphide (sulphuretted hydrogen).— This reagent may 
either be kept in the form of a saturated aqueous solution 
of the gas, or better, the gas may be freshly evolved as 
required. 


The special reagents pertaining to the analysis of 
glue and gelatine will be found under the specific 
determinations outlined in Chapter ITI. 

Quality of Reagents. Traces of metals presumably 
in the substance and determined in the course of an- 
alysis may often be traced to the reagents employed. 
A “ep.” (chemically pure) label is in no sense a 


APPENDIX 195 


guarantee of the purity of any reagent. For example, 
“e.p.”’ ammonium oxalate frequently contains traces 
of lime. Accordingly, reagents should be purified by 
recrystallization from their concentrated aqueous solu- 
tions, rejecting large crystals, as these are apt to 
contain too much of the mother liquor. These may, 
in turn, be recrystallized. The operator has, of 
course, to predetermine whether his work demands 
the highest accuracy or not. Upon his decision will 
depend the further purification of the reagents em- 
ployed for analytical work. 

Standard Solutions. — Standardized solutions of hy- 
drochloric acid, potassium hydroxide, and potassium 
permanganate are at almost all times required in the 
laboratory and should be prepared in quantity. 

(a) Hydrochloric acid (approximately decinormal). 

Forty grams of the chemically pure acid, specific 
gravity 1.12, are accurately weighed into a clean liter 
flask. This is then carefully made up to the mark, 
mixing the contents thoroughly. Ten such liters should 
be prepared and the whole mixed well in a bottle of 
ample capacity and well stoppered. 

To standardize this solution, proceed as follows : 
From a burette, run duplicate samples of 40 c. c. each 
of the acid solution, taking the reading carefully. To 
each sample add 20 c. c. nitric acid, and bring to in- 
cipient boiling. Add silver nitrate solution to each 
until no more precipitate forms, and stand the beakers 
in a dark place over night for the precipitate to settle. 
During the precipitation, it is well to exclude direct 
sunlight. Prepare two double filters, and pass the fil- 
trate through, holding back as much of the precipitate 


196 GLUES AND GELATINE 


as possible. Wash the filters well with boiling water 
containing 10 per cent of nitric acid, and with the same 
medium bring the precipitate onto the filters, washing 
the latter well between additions of precipitate. Rinse 
the beakers thoroughly of all precipitate and then wash 
filter and precipitate with plain boiling water until the 
washings are no longer turbid when treated with a drop 
of hydrochloric acid. 

Dry the precipitates upon the filters in the oven at 
100° C. (212° F). Prepare two porcelain crucibles, in- 
cinerate the filters as directed in the foregoing chapter, 
add the bulk of precipitate to the crucibles and warm 
with a small Bunsen flame. Gradually raise the flame 
until the precipitate of silver chloride just fuses at the 
edges. Place the crucibles in the desiccator and weigh 
the silver chloride. 

Calculate as follows: 


vse atomic] the ye | o of 


weight of weight of | .. found of . chlorine 
silver chlorine { ~ silver|. in it. 
chloride } ; chloride | 
The weight of chlorine 
No. c. c. HCl taken 


(b) Potassium Hydroxide (approximately decinormal.) 

Weigh out as closely as possible 7 grams pure caustic 
potash (precipitated by alcohol in sticks) into a clean 
liter flask, dissolve in a minimum of water, and make up 
to the mark, mixing well. About ten such liters should 
be prepared and mixed in a bottle of ample capacity. 

To standardize: 

(1) Against Oxalic Acid. 

Weigh out two portions, not more than 100 milli- 





=the mgs. chlorinein1 c.e. of acid. 


APPENDIX 197 


erams, of chemically pure oxalic acid that has been 
previously well powdered and dried to expel all water 
of crystallization. The samples are placed in beakers 
of 250 c. c. capacity, and dissolved by stirring in 150 
c. c. cold water. To each solution is added two drops 
of phenol-phthalein as indicator. The burette is now 
filled with the alkali solution, adjusted to zero, and the 
solution run into the oxalic acid drop by drop as the 
latter is stirred, until a pink coloration just appears. 
The reading is then accurately taken. 
Calculation: 


Molecular weight Twice the molecular weight] ‘ 
of oxalic acid of potassium hydroxide poe Ey 


where x = the weight of oxalic acid taken, 

and y = the weight of potassium hydroxide required 
to combine with z. 

Then y, divided by the number of ¢c. c. of potassa solu- 

tion taken = the number of milligrams of actual potas- 

stum hydroxide (KOH) in 1 e. ¢. solution. 

(2) Against Standard Acid. 

Fill two clean burettes, one with the standard acid 
solution, and the other with the unknown alkali. Select 
two Erlenmeyer flasks of about 250 c. c. capacity. 
Run into each 20 ec. ec. acid and add a few drops of 
litmus solution. Now run in the alkali, drop by drop, 
until the color of the solution in the flask turns from 
red to reddish blue, or violet. Boil the contents of 
the flask until all carbon dioxide is expelled, and add a 
few drops of alkali until the color of the solution is a 
true blue, without reddish cast. Note readings of 
both burettes. 


198 GLUES AND GELATINE 


Calculation: Assume, for example, that 30 c.c. 
alakli are required to neutralize 20 c. c. acid; whence, 
1c. c. alkali = 4 ¢.c.acid. Assumefurther that each c. c. 
standard acid = 3.65 milligrams HCl. Then each ec. ec. 
of alkali is equivalent to 2.48 milligrams hydrochloric 
acid. Since the reaction taking place is expressed 


HCl + KOH = KCl + H,0O, 
we have, 


mol. weight HCl : mol. weight KOH :: 2.48 : z, 
x = milligrams potassium hydroxide in each ec. ¢c. solution 


(c) Potassium permanganate. 

Weigh out 5 grams of chemically pure potassium 
permanganate into a clean beaker, and cover with cold 
water, stirring well. Permit the undissolved salt to 
subside and pour off the solution into a dark bottle, 
taking care that no undissolved portions are transferred 
with the solution. Again treat the salt in the beaker 
with water and again pour off, repeating the operation 
until all has been dissolved. ‘The total solution should 
not exceed 4 liters. 

To standardize: Secure some fine piano wire, which 
is virtually 99.6 per cent pure Jron. Clean this of any 
rust, by means of emory paper, and weigh out two por- 
tions of about 100 milligrams each. Place these in 
small beakers, add 20 c. c. concentrated hydrochloric 
acid, and heat cautiously until complete solution is 
effected. Cover the beaker with a watch-glass during 
the operation and subsequently rinse the glass into the 
beaker. Now add to the contents of the beaker a 
minute crystal of potassium chlorate and again warm 


APPENDIX / 199 


until the solution assumes the characteristic yellow 
color of ferric iron. ‘Transfer the contents of the beaker 
to a 250 c. c. Erlenmeyer flask, rinsing the beaker well. 
Support the flask so that it inclines at an angle of 45°, 
and let the contents boil gently until all oxides of chlorine 
have been expelled. In the interval, weigh out about 
5 grams chemically pure zinc spelter, selecting only 
thin, flat pieces. Add these cautiously to the contents 
of the flask. When the liberation of hydrogen subsides, 
add 40 c. ec. concentrated sulphuric acid to dissolve all 
residual zinc. The contents of the flask are now trans- 
ferred to a capacious beaker, the flask rinsed into same 
and the solution made up with 400 ec. c. additional 
_ water. : 

Fill a burette with the solution to be standardized. 
None but glass-stoppered burettes may be used for 
potassium permanganate solutions. Owing to the opacity 
of these solutions, they are extremely difficult to read 
without the aid of an Erdmann float. The permanga- 
nate is adjusted to the mark and run into the beaker 
drop by drop, with constant stirring, until a faint pink 
color is permanently established. The reading is then 
taken, and the weight of iron wire originally taken, 
divided by the number of ¢. c. permanganate solution 
run in, is expressed as the number of milligrams of tron, 
oxidized from the ferrous to the ferric state, by 1 c. c. per- 
manganate. 

It is to be noted that too much time must not be 
allowed to elapse between the reduction of the ferric 
iron to ferrous, and the titration with permanganate, 
else the solution is atmospherically re-oxidized to the 
ferric state and the reading of permanganate conse- 


200 GLUES AND GELATINE 


quently low. It should be seen that all zine is dissolved 
before transferring the contents of the flask to the beaker 
for titration, else these particles will reduce the solution 
as fast as it is oxidized by the permanganate. The 
results of the duplicate titrations should be fairly con- 
cordant, differing by not more than one part in 500. 


Comparison of English and Metric Weights 


1 milligram = .001 gram= .0154 troy grain= .00003 avoirdupois ounce 
1 centigram = .01 gram= .154 troy grain= .0003 avoirdupois ounce 
ldecigram = 1. gram= 1.540 troy grain= .003 avoirdupois ounce 
1 gram = 1.0 gram= 15.40 troy grain= <03 avoirdupois ounce 
ldecagram = 10.0 gram= 154.0 troy grain= .3 avoirdupois ounce 
1 hectogram= 100. gram= 1543.0 troy grain= 3.520 avoirdupois ounce 
1 kilogram =1000. gram= 15432. troy grain= 35.20 avoirdupois ounce 
1lkilogram = 2.2 pounds avoirdupois. 


1 Liter = 1000 c. c. = 14 quarts approximately. 
500 c. c. is approximately 1 pint. 

250 c. c. = approximately 8 oz. 

125 c. c. = approximately 4 oz. 


Comparison of Thermometers. 


To convert degrees Fahrenheit into degrees Centigrade, 
subtract 32 and multiply by 3. 
Example: Convert 212° F. into degrees C. 


212 — 32 =180. 180X 8 =100. Ans., 100°C. 


To convert degrees Centigrade into degrees Fahrenheit, 
multiply by 2 and add 32. 
Example: Convert 15° C. into degrees Fahrenheit. 


15 X & = 27. -27 4+ 82 = 50. Angee 


APPENDIX 201 


EQUIVALENT OF DEGREES BEAUME, AMERICAN STAND- 
ARD, AND SPECIFIC GRAVITY AT 60° F.* 











(a) For Liquips HEAVIER THAN Water, BeaumiE= 145 — 5% 
AAG 3 y= 
Degrees Specific Degrees Specific Degrees Specific 
Beaumé Gravity Beaumé Gravity Beaumé Gravity 
0 1.0000 24 1.1983 48 1.4948 
1 1.0069 20 1.2083 49 1.5104 
12 1.0140 26 1.2185 50 1.5263 
3 1.0211 27 1.2288 5} 1.5426 
4 1.0284 28 1.2393 52 1.5591 
5 1.0357 29 1.2500 53 1.5761 
6 1.0432 30 1.2609 54 1.5934 
t 1.0507 31 1.2719 55 Leol ls 
8 1.0584 32 1.2832 56 1.6292 
9 1.0662 oa 1.2946 oF 1.6477 
10 1.0741 34 1.3063 58 1.6667 
11 1.0821 35 1.3182 59 1.6860 
12 1.0902 36 1.3303 60 1.7059 
13 1.0985 37 1.3426 61 127262 
14 1.1069 38 1.3551 62 1.7470 
15 11154 39 1.3679 63 1.7683 
16 1.1240 40 1.3810 64 1.7901 
17 121328 41 1.3942 65 1.8125 
18 14% 42 1.4078 66 1.8354 
19 1.1508, 43 1.4216 67 1.8590 
20 1.1600 44 1.4356 68 1.8831 
21 1.1694 45 1.4500 69 1.9079 
22 1.1789 46 1.4646 70 1.9333 
23 1.1885 47 1.4796 


* Chemical Annual. 


202 GLUES AND GELATINE 


EQUIVALENT OF DEGREES BEAUMf, AMERICAN STAND- 
- ARD, AND SPECIFIC GRAVITY AT 60° F.* 


140 

(b) For Liquins LIGHTER THan WartsER, Sp. Gr. 130 4. Be® 

Degrees Specific Degrees Specific Degrees Specific 

Beaumé Gravity Beaumé Gravity Beaumé Gravity 
10 1.0000 34 0.8537 58 0.7447 
11 0.9929 35 0.8485 59 0.7407 
12 0.9859 36 0.8434 60 0.7368 
13 0.9790 37 0. 8383 61 0.7330 
14 0.9722 38 0.8333 62 0.7292 
15 0.9655 39 0.8284 63 0.7254 
16 0.9589 40 0.8235 64 0.7216 
17 0.9524 41 0.8187 65 0.7179 
18 0.9459 42 0.8140 66 0.7143 
19 0.9396 43 0. 8092 67 0.7107 
20 0.9333 44 0.8046 68 0.7071 
21 0.9272 45 0. 8000 69 0.7035 
22 0.9211 46 0.7955 70 0.7000 
23 0.9150 47 0.7910 71 0.6965 
24 0.9091 48 0.7865 72 0.6931 
25 0.9032 49 0.7821 73 0.6897 
26 0.8974 50 0.7778 74 0.6863 
27 0.8917 51 0.7735 75 0.6829 
28 0.8861 52 0.7692 76 0.6796 
29 0.8805 53 0.7650 ‘iti 0.6763 
30 0.8750 54 0.7609 78 -0.6731 
31 0.8696 55 0.7568 79 0.6699 
32 0.8642 56 0.7527 80 0.6667 
33 0.8589 57 0.7487 


* Chemical Annual. 


To Convert Specific Gravity into Degrees Twaddle. 


Multiply by 1000, subtract 1000, and divide by 5. 
Example: Convert 1.250 sp. gr. into degrees Twaddle. 


APPENDIX 


1.250 x 1000 = 1250 
1000 
5)250 

Ans. = 50° Tw. 





To Convert Degrees Twaddle into Specific Gravity. 


Multiply by 5, add 1000, and divide by 1000. 
Example: Convert 125° Tw. into specific gravity. 


125x5 = 625 
1000 
1000)1625 


Ans. = 1.625 specific gravity. 


203 


204 


GLUES AND GELATINE 


TABLE OF INTERNATIONAL ATOMIC WEIGHTS 





Aluminium 
Antimony 
Argon 
Arsenic 
Barium 
Bismuth 
Boron 
Bromine 
Cadmium 
Cesium 
Calcium 
Carbon 
Cerium 
Chlorine 
Chromium 
Cobalt 
Columbium 
(Niobium) 
Copper 
Erbium 
Fluorine 
Gadolinium 
Gallium 
Germanium 
Glucinum 
(Beryllium) 
Gold 
Helium 
Hydrogen 
Indium 
Iodine 
Iridium 
Tron 
Krypton 
Lathanum 
Lead 
Lithium 
Magnesium 
Manganese 
Mercury 


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Gl 9.1 
197.2 
4.0 
H | 1.008 
114.0 
I. 1426.8 
Ir | 193.0 
55.9 
81.8 
138.9 
206.9 
Li Yeas k 
24.4 
Mn| 55.0 
Hg} 200.0 


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Molybdenum 
Neodymium 
Neon 

Nickel 
Nitrogen 
Osmium 
Oxygen 
Palladium 
Phosphorus 
Platinum 
Potassium 


Praseodymium 


Radium 
Rhodium 
Rubidium 
Ruthenium 
Samarium 
Scandium 
Selenium 
Silicon 
Silver 
Sodium 
Strontium 
Sulphur 
Tantalum 
Tellurium 
Terbium 
Thallium 
Thorium 
Thulium 
Tin 
Titanium 
Tungsten 
Uranium 
Vanadium 
Xenon 
Ytterbium 
Yttrium 
Zine 
Zirconium 


O= 1610 = 
Mo| 96.0] 95.3 
Nd| 143.6 | 142.5 
Ne! 20.0! 19.9 
Ni| 58.7] 58.3 
N | 14.1] 13.9 
Os! 191.0] 189.6 
O |. 16:0) 215-8 
Pd| 106.5 | 105.7 
P| 3120304 
Pt )194.8| 193.3 
K | 39.1] 38.8 
Pr | 140.5| 139.4 
Ra| 225.0 | 223.3 
Rh] 103.0] 102.2 
Rb| 85.4] 84.8 
Rul] 101.7 | 100.9 
Sm] 150.0) 148.9 
Sc} 44.1] 43.8 
Se | 79.2] 78.6 
Si | 28.4] 28.2 
Ag| 107.9 | 107.1 
Nal 23.1. 22:8 
Sr | 87.6] 86.9 
S 4 S214 eeira 
Ta] 183.0] 181.6 
Te| 127.6 | 126.6 
Tb] 160.0| 158.8 
Tl | 204.1 | 202.6 
Th] 232.5| 230 8 
Tm] 171.0 | 169.7 
Sn} 119.0} 118.1 
TT PASAT 
W | 184.0| 182.6 
U | 238.5 | 236.7 
V | 51.2! 50.8 
X | 128.0) 127.0 
Yb| 173.0/ 171.7 


Yt} 89.0] 88.3 
Zn| 65.4| 64.9 
Zr| 90.6} 89.9 





INDEX 


PAGE 


Acid, carbolic 12 
hydrochloric, standard 195 
hydrofluoric 12 
salicylic 12 
soaps 9 
sulphuric < 
sulphurous 13 
tannic 70 
-treated glue 9 


Acidity, determination of 61 
of wall-paper glues 118 
28 


test for 

Acids, free organic 62 
mineral 28 
Adhesiveness of glue 142 
Adulteration of glue 72, 132 
Agar-Agar 4179 
Air drying, of glue 14 
Albumen 75 
Albumin, analysis of 82 
sage 75 
egg- 75 
Alcoholic potash 191 

Alkalinity, determination 
of 61 
of wall-paper glues 118 
test for 28 
Alum, in glue 61 
Analysis of glue 58 
Analytical processes 175 
Animal glue 1 
Apparatus, analytical 174 
for glue testing 50 
volumetric 189 
volumetric, cleaning 191 
Ash, analysis of 60 
‘determination of 59 
Atomic weights 204 
Bacteria, of decomposition 3 
Bacterium lactis 73 
Balance, care of the 176 

Beaumé degrees, table of 
201, 202 


PAGE 
Belt cement 161 
Bichromate of potash 192 
Bleaching 13 
Block C 95 
Block CL 96 
Blood-albumin 75 
Boiling, effect of on glue 11, 137 
Boiling glue stock 10 
Bone, cement for 162 
Bone glue 9 
distinction from hide 60 
Bones. as glue stock AY 
as gelatine stock 5 
junk 9 
treatment of 8,9 
Box-maker’s glue 125, 164 
Breaking strain of glue 20 
Burette, the 190 
Cabinet glues 146, 148, 149 
Casein 73 
examination of 82 
Cement, for bone 162 
for glass 160 
for iron 158 
for ivory 162 
for knife-handles 162 
for leather 161 
for metals 158 
for pipe-joints 159 
for porcelain 159 
for wood 162 
Chondrin 3, 4 
preparation of 66 
reactions of 67 
Clarified glue 61 
Colors, pulp 112-117 
Comparison, foreign and 
domestic glue 86 
Composition, padding 163 
colored 164 
white 163 . 
Concentrated size 94 
Consumer, glue 145-149 


205 


206 INDEX 
PAGE E PAGE 
Consumer’s legal redress 154 | Gelatin 2,4 
Cooper grades 22 estimation of 64 
viscosity of 40 preparation of 64, 65 
Cut of glue 16 reactions of 65 
fa ape oe h at Gel ramet ei of oy 
the elatine, 
Cylinder, graduated fae : 5 
: groun 5) 
Degreasing 8 Japanese 2, 78, 85 
Desiccation 175 powdered 
Dextrin 84 shane 15 
Dextrines 77, 84 ahned 15 
Dextrine mucilage 170 strip 15 
Diamond cement 159 substitutes 72-85 
Dissolving glue 136 Gelose 1, 78 
Domestic glues 93 | Glasses, for test 50 
Drying glue jelly 14 Clad: 2,79 
Glue, acid-treated 9 
Egg-albumin 75 adulteration of 72,132 
Estimation, of acidity 61 analysis of 58 
of alkalinity 63 cabinet 146, 148, 149 
of fat 63 clarified 61 
of foreign matter 70 colored 7 
of gelatin 64 coloring of 12, 13 
of glue-content 67 content 
of grease 63 cost of 149 
of jelly-strength 45 cut of 16 
of moisture 59 cutting | F ue 
Evaporating glue liquors 13 pay yy ' 4 
Examination of dry glue 21, 23 Ringlian 94 
fish 18 
Fatty acids e:}) flake 15 
Fehling’s solution 85 flexible 19, 163 
Fernbach’s viscosimeter 37 foam in 44 
Filters, incineration of 188 for joiner work 105 
Filtration 185 for matches 131 
Finger test 47 for paper boxes 125 
Fish glue 18 for sizing work 126 
Flasks, volumetric 191 for surface-coated 
Flexible glue 163 papers 123 
Flour pastes 79, 167 for textiles 128 
Foam, in wall-paper glues 120 for wall papers 110 
test for 44 foreign 86 
Foreign glues 86 forms of 15 
Foreign matter 70 French 99 
Formaldehyde 12 frozen 14 
Forms of glue 15 German 97 
Free acid . 28 grease in 30, 63 
organic 62 ground 15 
French glue 99 mixed : 132 © 
Frozen glue 14 hide 5 


INDEX 207 
PAGE AGE 
Glue — continued. Greasy tops and bottoms 15 
Trish 95 | Gum, arabic 78, 171 
Italian 102 Boston 81 
ying f 13 box-toe 172 
jobber 51 Brightwood 81 
liquid 19, 80, 164 tragacanth 1; 170 
manufacture of 5 
eve 53, aH Heating glue, loss of te- 
pose te Te ete ee! due to a af 
ee 17 distinction from bone 60 
Patni eS Hide pieces 5 
: splits 5 
over-limed 29 stock, liming 6 
powdered 15 washing 
SA a aa Holding power, of wood 
Russian 103 | Hot SiS eee 106 
sampling 24 : 
cenpitd ot sas Indicators 191 
Cerrated 16 | Ish glue 95 
soaking PLE ae aan 1,78 
solution, acidity of 28 Italiy ig 18 
alkalinity of 28 eee glue 102 
solution, odor of 27 vory, glue for 162 
f : 
Seeder 5 ee gelatine 1; 78, 85 
Eelnetion of 52 ellies, glue, cooling 53 
strip 15 | Jelling glue 13 
substitutes 72, 85 | Jelly-strength a5 
testing 90-57 | Joimer’s glue 105 
thimble 16 | Joints, holding power of 
true, distinction of 12 glue 106 
waste of 140 ; 
water-proof substitutes Keratin 3 
157, 158 
white 17, 148 | Leather, cement for 161 
Glue-liquor, bleaching 13 | Legal redress, consumer’s 154 
coloring 13 | Library paste 165 
jelling 13 | Liming 6 
preserving 12 | Lime soaps 42 
Glue-stock, blending 9 | Lipowitz’ shot test 46 
boiling 10 | “Liquid” glue 164 
liming 6 | Liquid glues 19, 80, 164 
2 washing 8 | Liquids, weighing out 185 
uten 79 
Grades, Cooper 22 | Manufacture of glue 2 
Grease, estimation of — 63 | Manufacturing receipts 157 
in wall-paper glue 118 | Marine glue 158 
paper g 
recovery of 10 | Melting bath 51 
test for 30 !' Melting glue 53, 137 


208 INDEX 
PAGE PAGE 
Melting pot, cleaning 140 | Soaps, acid 9 
Metric weights 200 lime 42 
Mineral acidity 28 | Softening glue 52, 136 
oils 145 | Solutions, standard 195 
Moisture in glue 59 | Sources of glue + 
Mucilage, dextrine 170 | Specific gravity, tables 201, 202 
gum arabic 171 conversion to ° Tw. 202, 203 
Mucin 3 | Specifications for glue 146, 149 
reactions of 67 | Sulphuric acid i 
Sulphurous acid 13 
Oil cements 159 | Starch pastes 166 
Oils, mineral 145 
Over-liming 7 | Tannate of gelatin 67 
Tannic acid 70 
Padding composition 163 | Test methods 23 
Paste, flour 79, 167 record 56 
Pastes, starch 166 recording 54 
Photo-library paste 165 system . 48 
Pipette, the 189 Thermometers, compari- 
viscosity 34, 37 _ _ son of 
Position of rest 178 | Thimble glue 16 
Potash, alcoholic 191 | Titration 190 
Potassium, hydroxide, Twaddle, conversion to 
standard 196 sp. gr. 202, 203 
permanganate, standard 198 
Precipitates, drying 188 | Vacuum evaporator 13 
incineration of 188 | Vegetable agglutinants 1 
washing 187 | Viscosimeter, simple 34, 37 
Prepared size 171 Fernbach’s 37, 38 
Processes, analytical 175 | Viscosity 3 
volumetric 189 of acid-treated glues 41 
Pulp-colors 112-117 of colored glues 41 
Purity of gelatine 58, 71 of Cooper grades 40 
of glue 58 wall paper glues 121 
wares tables of 43 
Rating glues 147 value O1, as a test 
Reagents 175, 193, 194 factor 39 
quality of 194 
Recovery, of glue 140 | Wall-paper glues 110 
of grease 10 -} Weighing tes 176 
Runs, in glue boiling 11, 12 by half differences 180 
Russian glue 103 glues for test 52 
me of 176 
Samples, preparation of 182 iquids 185 
SEAT mS 24 potash bulbs 185 
Scarcity of glue 149 _U tubes 185 
Scotch glue 96 | White glues 17, 148 
Serrated glue 16 
Size, concentrated 94 | Zinc oxide 13 
prepared 171 sulphate 14 
Sizing, glue for 126 white 13 


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